{"id":953,"date":"2025-12-24T17:18:16","date_gmt":"2025-12-24T08:18:16","guid":{"rendered":"https:\/\/math-travel.com\/?p=953"},"modified":"2026-02-28T15:37:05","modified_gmt":"2026-02-28T06:37:05","slug":"discriminant","status":"publish","type":"post","link":"https:\/\/math-travel.jp\/math-1\/discriminant\/","title":{"rendered":"\u5224\u5225\u5f0fD\u306e\u516c\u5f0f\u3068\u4f7f\u3044\u65b9\uff01\u5b9f\u6570\u89e3\u30fb\u5171\u6709\u70b9\u306e\u500b\u6570\u3092\u898b\u5206\u3051\u308b\u65b9\u6cd5\u3092\u7df4\u7fd2\u554f\u984c\u3067\u89e3\u8aac"},"content":{"rendered":"\n<p>\u6570\u5b66\u2160\u4e8c\u6b21\u95a2\u6570\u306e\u516c\u5f0f\u306e\u306a\u304b\u3067\u3082\u300c\u5224\u5225\u5f0fD\u300d\u306f\u91cd\u8981\u306a\u516c\u5f0f\u3067\u3059\u3002<\/p>\n\n\n\n<div class=\"wp-block-group has-border -border01\"><div class=\"wp-block-group__inner-container is-layout-constrained wp-block-group-is-layout-constrained\">\n<p><span class=\"huto\">\u300c\u5224\u5225\u5f0fD\u3068\u306f\uff1f\u300d<\/span><br><span class=\"huto\">\u300c\u5224\u5225\u5f0f\u3092\u4f7f\u3063\u3066\u89e3\u306e\u500b\u6570\u3092\u6c42\u3081\u305f\u3044\u300d<\/span><\/p>\n<\/div><\/div>\n\n\n\n<p>\u9ad8\u6821\u6570\u5b66\u306b\u304a\u3044\u3066\u3001\u5224\u5225\u5f0fD\u306f\u975e\u5e38\u306b\u91cd\u8981\u306a\u516c\u5f0f\u306e1\u3064\u3067\u3059\u3002<\/p>\n\n\n\n<p>\u5224\u5225\u5f0fD\u3092\u6c42\u3081\u308b\u516c\u5f0f\u306f\u4ee5\u4e0b\u306e\u901a\u308a\u3067\u3059\u3002<\/p>\n\n\n\n<div class=\"swell-block-capbox cap_box\"><div class=\"cap_box_ttl\"><span><span class=\"huto\">\u5224\u5225\u5f0fD\u306e\u516c\u5f0f<\/span><\/span><\/div><div class=\"cap_box_content\">\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"542\" height=\"162\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u306e\u516c\u5f0f-1.png\" alt=\"\u5224\u5225\u5f0fD\u306e\u516c\u5f0f\" class=\"wp-image-7231\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u306e\u516c\u5f0f-1.png 542w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u306e\u516c\u5f0f-1-300x90.png 300w\" sizes=\"auto, (max-width: 542px) 100vw, 542px\" \/><\/figure>\n\n\n\n<p class=\"has-text-align-center\">\u5224\u5225\u5f0f\\(D=b^{2}-4ac\\)<\/p>\n<\/div><\/div>\n\n\n\n<p>\u5224\u5225\u5f0fD\u3092\u5229\u7528\u3059\u308b\u3053\u3068\u3067\u3001<span class=\"huto\"><span class=\"yellow-hoso\">\u4e8c\u6b21\u65b9\u7a0b\u5f0f\u306e\u5b9f\u6570\u89e3\u306e\u500b\u6570<\/span><\/span>\u304c\u5206\u304b\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"756\" height=\"386\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u95a2\u6570\u306e\u5224\u5225\u5f0f.png\" alt=\"2\u6b21\u95a2\u6570\u306e\u5224\u5225\u5f0f\" class=\"wp-image-5603\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u95a2\u6570\u306e\u5224\u5225\u5f0f.png 756w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u95a2\u6570\u306e\u5224\u5225\u5f0f-300x153.png 300w\" sizes=\"auto, (max-width: 756px) 100vw, 756px\" \/><\/figure>\n\n\n\n<p><a href=\"#mondai\">\u226b\u5224\u5225\u5f0fD\u3092\u4f7f\u3063\u305f\u7df4\u7fd2\u554f\u984c\u306f\u3053\u3061\u3089<\/a><\/p>\n\n\n\n<p>\u672c\u8a18\u4e8b\u3067\u306f\u3001\u5224\u5225\u5f0fD\u306e\u516c\u5f0f\u3068\u89e3\u306e\u500b\u6570\u3068\u306e\u95a2\u4fc2\u306b\u3064\u3044\u3066\u89e3\u8aac\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"Dtoha\">\u5224\u5225\u5f0fD\u3068\u306f\uff1f\u516c\u5f0f\u3092\u899a\u3048\u3088\u3046<\/h2>\n\n\n\n<p>\u307e\u305a<span class=\"huto\">\u5224\u5225\u5f0fD<\/span>\u3068\u306f\u4ee5\u4e0b\u306e\u516c\u5f0f\u3092\u6307\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n\n\n<div class=\"wp-block-image wp-image-7231 size-full\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"542\" height=\"162\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u306e\u516c\u5f0f-1.png\" alt=\"\u5224\u5225\u5f0f\u306e\u516c\u5f0f\" class=\"wp-image-7231\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u306e\u516c\u5f0f-1.png 542w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u306e\u516c\u5f0f-1-300x90.png 300w\" sizes=\"auto, (max-width: 542px) 100vw, 542px\" \/><figcaption class=\"wp-element-caption\">\u300a\u5224\u5225\u5f0fD\u306e\u516c\u5f0f\u300b<\/figcaption><\/figure>\n<\/div>\n\n\n<p>\u4e8c\u6b21\u65b9\u7a0b\u5f0f\u306b\u304a\u3051\u308b\u5404\u9805\u306e\u4fc2\u6570\u3092\\(a,b,c\\)\u3068\u3057\u3066\u3001<\/p>\n\n\n\n<div class=\"swell-block-capbox cap_box\"><div class=\"cap_box_ttl\"><span>\u5224\u5225\u5f0fD\u306e\u516c\u5f0f<\/span><\/div><div class=\"cap_box_content\">\n<p>\\(y=ax^2+bx+c\\)\u306e\u3068\u304d\u5224\u5225\u5f0f(D)\u306f<\/p>\n\n\n\n<p>\\[D=b^{2}-4ac\\]<\/p>\n<\/div><\/div>\n\n\n\n<p>\u5404\u5024\u3092\\(a,b,c\\)\u306b\u4ee3\u5165\u3059\u308b\u3053\u3068\u3067\u3001D\u306e\u5024\u3092\u6c42\u3081\u307e\u3059\u3002<\/p>\n\n\n\n<p>\u3053\u306e\u5224\u5225\u5f0fD\u306e\u7b26\u53f7\u306b\u3088\u3063\u3066\u3001<span class=\"huto\">\u4e8c\u6b21\u65b9\u7a0b\u5f0f\u304c\u5b9f\u6570\u89e3\u3092\u3044\u304f\u3064\u6301\u3064\u306e\u304b<\/span>\u3092\u5224\u65ad\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n\n\n<div class=\"swell-block-balloon\"><div class=\"c-balloon -bln-right\" data-col=\"gray\"><div class=\"c-balloon__icon -circle\"><img decoding=\"async\" loading=\"lazy\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2024\/05\/math-travel-hukidashi1-150x150.webp\" alt=\"\" class=\"c-balloon__iconImg\" width=\"80px\" height=\"80px\"><span class=\"c-balloon__iconName\">\u30b7\u30fc\u30bf<\/span><\/div><div class=\"c-balloon__body -speaking -border-on\"><div class=\"c-balloon__text\">\n<p>D\u306e\u7b26\u53f7\u304c\u3069\u3046\u306a\u308b\u304b\u306b\u6ce8\u76ee\u3059\u308b\u3093\u3060\u306d<\/p>\n<span class=\"c-balloon__shapes\"><span class=\"c-balloon__before\"><\/span><span class=\"c-balloon__after\"><\/span><\/span><\/div><\/div><\/div><\/div>\n\n\n<h2 class=\"wp-block-heading\" id=\"kai\">\u5224\u5225\u5f0fD\u3068\u5b9f\u6570\u89e3\u306e\u500b\u6570<\/h2>\n\n\n\n<p>\u5224\u5225\u5f0fD\u306e\u7b26\u53f7\u306b\u3088\u3063\u3066\u5b9f\u6570\u89e3\u306e\u500b\u6570\u304c\u5206\u304b\u308b\u3068\u66f8\u304d\u307e\u3057\u305f\u304c\u3001\u3082\u3046\u5c11\u3057\u6df1\u6398\u308a\u3057\u3066\u89e3\u8aac\u3057\u307e\u3059\u3002<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"756\" height=\"386\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u95a2\u6570\u306e\u5224\u5225\u5f0f.png\" alt=\"\" class=\"wp-image-5603\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u95a2\u6570\u306e\u5224\u5225\u5f0f.png 756w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u95a2\u6570\u306e\u5224\u5225\u5f0f-300x153.png 300w\" sizes=\"auto, (max-width: 756px) 100vw, 756px\" \/><\/figure>\n<\/div>\n\n\n<div class=\"swell-block-capbox cap_box is-style-onborder_ttl2\"><div class=\"cap_box_ttl\"><span>\u5224\u5225\u5f0fD\u3068\u89e3\u306e\u500b\u6570<\/span><\/div><div class=\"cap_box_content\">\n<p>D&gt;0\u306e\u3068\u304d\u3001\u7570\u306a\u308b\u5b9f\u6570\u89e3\u30922\u3064\u3082\u3064\u3002<br>D=\u306e\u3068\u304d\u3001\u5b9f\u6570\u89e3\u30921\u3064\u3082\u3064\u3002\uff08\u91cd\u89e3\uff09<br>D&lt;0\u306e\u3068\u304d\u3001\u5b9f\u6570\u89e3\u3092\u3082\u305f\u306a\u3044\u3002<\/p>\n<\/div><\/div>\n\n\n\n<p>\u8a00\u8449\u3060\u3051\u3067\u306f\u30d4\u30f3\u3068\u3053\u306a\u3044\u3068\u601d\u3046\u306e\u3067\u3001\u5b9f\u969b\u306b\u6570\u5b57\u3092\u5165\u308c\u3066\u8003\u3048\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n\n\n\n<div class=\"swell-block-capbox cap_box is-style-inner\"><div class=\"cap_box_ttl\"><span>\u4f8b\u984c\uff11<\/span><\/div><div class=\"cap_box_content\">\n<p>2\u6b21\u65b9\u7a0b\u5f0f\\(x^{2}+2x-3=0\\)\u306e\u5b9f\u6570\u89e3\u306e\u500b\u6570\u3092\u6c42\u3081\u3088\u3046\u3002<\/p>\n<\/div><\/div>\n\n\n\n<div class=\"wp-block-group is-style-bg_stripe\"><div class=\"wp-block-group__inner-container is-layout-constrained wp-block-group-is-layout-constrained\">\n<p>2\u6b21\u65b9\u7a0b\u5f0f\\(x^{2}+2x-3=0\\)\u306e\u5224\u5225\u5f0f\u3092D\u3068\u3059\u308b\u3068<\/p>\n\n\n\n<p>\\[D=2^{2}-4 \\cdot 1 \\cdot (-3)=16&gt;0\\]<\/p>\n\n\n\n<p>\\(D&gt;0\\)\u306a\u306e\u3067\u3001<span class=\"huto\">\u5b9f\u6570\u89e3\u306e\u500b\u6570\u306f2\u500b\u3067\u3042\u308b\u3002<\/span><\/p>\n<\/div><\/div>\n\n\n<div class=\"swell-block-balloon\"><div class=\"c-balloon -bln-left\" data-col=\"gray\"><div class=\"c-balloon__icon -circle\"><img decoding=\"async\" loading=\"lazy\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2024\/05\/math-travel-hukidashi7-150x150.webp\" alt=\"\" class=\"c-balloon__iconImg\" width=\"80px\" height=\"80px\"><span class=\"c-balloon__iconName\">\u9ad8\u6821\u751f<\/span><\/div><div class=\"c-balloon__body -speaking -border-on\"><div class=\"c-balloon__text\">\n<p>\u6570\u5b57\u3092\u4ee3\u5165\u3059\u308b\u3060\u3051\u306a\u3093\u3060\u306d\uff01<\/p>\n<span class=\"c-balloon__shapes\"><span class=\"c-balloon__before\"><\/span><span class=\"c-balloon__after\"><\/span><\/span><\/div><\/div><\/div><\/div>\n\n\n<h2 class=\"wp-block-heading\" id=\"kyouyuu\">\u5224\u5225\u5f0fD\u3068\u5171\u6709\u70b9\u306e\u500b\u6570<\/h2>\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"1200\" height=\"655\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2026\/02\/discriminant-ill_0.webp\" alt=\"\u5224\u5225\u5f0fD\u306e\u7b26\u53f7\u306b\u3088\u308b2\u6b21\u95a2\u6570\u30b0\u30e9\u30d5\u3068x\u8ef8\u306e\u5171\u6709\u70b9\uff082\u500b\u30fb1\u500b\u30fb0\u500b\uff09\u306e\u5bfe\u5fdc\u56f3\" class=\"wp-image-21574\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2026\/02\/discriminant-ill_0.webp 1200w, https:\/\/math-travel.jp\/wp-content\/uploads\/2026\/02\/discriminant-ill_0-768x419.webp 768w\" sizes=\"(max-width: 1200px) 100vw, 1200px\" \/><\/figure>\n\n\n\n\n\n<p>\u5224\u5225\u5f0fD\u306e\u7b26\u53f7\u306b\u3088\u3063\u3066\u3001<span class=\"huto\"><span class=\"yellow-hoso\">2\u6b21\u95a2\u6570\u3068x\u8ef8\u3068\u306e\u5171\u6709\u70b9\u306e\u500b\u6570<\/span><\/span>\u304c\u5206\u304b\u308a\u307e\u3059\u3002<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"746\" height=\"256\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u65b9\u7a0b\u5f0f\u306e\u89e3.png\" alt=\"2\u6b21\u65b9\u7a0b\u5f0f\u306e\u89e3\" class=\"wp-image-5604\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u65b9\u7a0b\u5f0f\u306e\u89e3.png 746w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u65b9\u7a0b\u5f0f\u306e\u89e3-300x103.png 300w\" sizes=\"auto, (max-width: 746px) 100vw, 746px\" \/><\/figure>\n<\/div>\n\n\n<p>\u3064\u307e\u308a\u3001\u5224\u5225\u5f0fD\u306e\u7b26\u53f7\u306b\u3088\u3063\u3066\u4ee5\u4e0b\u306e3\u3064\u306e\u3053\u3068\u304c\u3044\u3048\u307e\u3059\u3002<\/p>\n\n\n\n<div class=\"swell-block-capbox cap_box\"><div class=\"cap_box_ttl\"><span>\u5224\u5225\u5f0fD\u3068x\u8ef8\u3068\u306e\u95a2\u4fc2<\/span><\/div><div class=\"cap_box_content\">\n<p>\u2460D&gt;0\u306e\u3068\u304d\u3001\u4e8c\u6b21\u65b9\u7a0b\u5f0f\u306f\u7570\u306a\u308b2\u3064\u306b\u5b9f\u6570\u89e3\u3092\u3082\u3064\u306e\u3067\u3001x\u8ef8\u30682\u304b\u6240\u3067\u4ea4\u308f\u308b\u3002<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"788\" height=\"285\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f\u3000\u4ea4\u70b9\u306e\u500b\u6570.jpg\" alt=\"\" class=\"wp-image-969\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f\u3000\u4ea4\u70b9\u306e\u500b\u6570.jpg 788w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f\u3000\u4ea4\u70b9\u306e\u500b\u6570-300x109.jpg 300w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f\u3000\u4ea4\u70b9\u306e\u500b\u6570-768x278.jpg 768w\" sizes=\"auto, (max-width: 788px) 100vw, 788px\" \/><\/figure>\n<\/div>\n\n\n<p>\u2461D=0\u306e\u3068\u304d\u3001\u4e8c\u6b21\u65b9\u7a0b\u5f0f\u306f1\u3064\u306e\u5b9f\u6570\u89e3\u3092\u3082\u3064\u306e\u3067\u3001x\u8ef8\u3068\u63a5\u3057\u3066\u3044\u308b\u3002<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"779\" height=\"240\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f\u3000\u4ea4\u70b9\u306e\u500b\u6570\u3000\u91cd\u8907.jpg\" alt=\"\" class=\"wp-image-968\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f\u3000\u4ea4\u70b9\u306e\u500b\u6570\u3000\u91cd\u8907.jpg 779w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f\u3000\u4ea4\u70b9\u306e\u500b\u6570\u3000\u91cd\u8907-300x92.jpg 300w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f\u3000\u4ea4\u70b9\u306e\u500b\u6570\u3000\u91cd\u8907-768x237.jpg 768w\" sizes=\"auto, (max-width: 779px) 100vw, 779px\" \/><\/figure>\n<\/div>\n\n\n<p>\u2462D&lt;0\u306e\u3068\u304d\u3001\u4e8c\u6b21\u65b9\u7a0b\u5f0f\u306f\u5b9f\u6570\u89e3\u3092\u3082\u305f\u306a\u3044\u306e\u3067x\u8ef8\u3068\u306f\u4ea4\u308f\u3089\u306a\u3044\u3002<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"608\" height=\"250\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f\u3000\u4ea4\u70b9\u306e\u500b\u6570\u3000\u865a\u6570.jpg\" alt=\"\" class=\"wp-image-967\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f\u3000\u4ea4\u70b9\u306e\u500b\u6570\u3000\u865a\u6570.jpg 608w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f\u3000\u4ea4\u70b9\u306e\u500b\u6570\u3000\u865a\u6570-300x123.jpg 300w\" sizes=\"auto, (max-width: 608px) 100vw, 608px\" \/><\/figure>\n<\/div><\/div><\/div>\n\n\n<div class=\"swell-block-balloon\"><div class=\"c-balloon -bln-right\" data-col=\"gray\"><div class=\"c-balloon__icon -circle\"><img decoding=\"async\" loading=\"lazy\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2024\/05\/math-travel-hukidashi1-150x150.webp\" alt=\"\" class=\"c-balloon__iconImg\" width=\"80px\" height=\"80px\"><span class=\"c-balloon__iconName\">\u30b7\u30fc\u30bf<\/span><\/div><div class=\"c-balloon__body -speaking -border-on\"><div class=\"c-balloon__text\">\n<p>\u96e3\u3057\u304f\u611f\u3058\u307e\u3059\u304c\u3001\u5185\u5bb9\u306f\u5358\u7d14\u306a\u306e\u3067\u5b89\u5fc3\u3057\u3066\u306d\u3002<\/p>\n<span class=\"c-balloon__shapes\"><span class=\"c-balloon__before\"><\/span><span class=\"c-balloon__after\"><\/span><\/span><\/div><\/div><\/div><\/div>\n\n\n<p>\u305d\u3082\u305d\u3082\\(ax^{2}+bx+c=0\\)\u3068\u3044\u3046\u306e\u306f\u3001<br>\\(y=ax^{2}+bx+c\\)\u3068x\u8ef8\u306e\u4ea4\u70b9\u306ex\u5ea7\u6a19\u3092\u6c42\u3081\u3066\u3044\u307e\u3059\u3002<\/p>\n\n\n\n<p>\u3069\u3046\u3044\u3046\u3053\u3068\u304b\u3068\u8a00\u3046\u3068<br>2\u6b21\u65b9\u7a0b\u5f0f\\(x^{2}-6x+8=0\\)\u3092\u4f8b\u3068\u3057\u3066<\/p>\n\n\n\n<p>\\begin{eqnarray}<br>x^{2}-6x+8&amp;=&amp;0\\\\<br>(x-2)(x-4)&amp;=&amp;0\\\\<br>x&amp;=&amp;2,4<br>\\end{eqnarray}<\/p>\n\n\n\n<p>\u3068\u306a\u308a\u307e\u3059\u304c\u3001<\/p>\n\n\n\n<p>\u3053\u308c\u306f2\u6b21\u95a2\u6570\\(y=x^{2}-6x+8\\)\u304c\\(x=2,4\\)\u3067x\u8ef8\u3068\u4ea4\u308f\u308b\u3053\u3068\u3092\u8868\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"428\" height=\"291\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u3068x\u8ef8\u306e\u4ea4\u70b9.png\" alt=\"\u5224\u5225\u5f0f\u3068x\u8ef8\u306e\u4ea4\u70b9\" class=\"wp-image-5605\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u3068x\u8ef8\u306e\u4ea4\u70b9.png 428w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u3068x\u8ef8\u306e\u4ea4\u70b9-300x204.png 300w\" sizes=\"auto, (max-width: 428px) 100vw, 428px\" \/><\/figure>\n<\/div>\n\n\n<p>2\u6b21\u65b9\u7a0b\u5f0f\u306e\u89e3\u304c\u4f55\u3092\u8868\u3057\u3066\u3044\u308b\u306e\u304b\u3001\u3057\u3063\u304b\u308a\u7406\u89e3\u3057\u3066\u3044\u308b\u5b66\u751f\u306f\u5c11\u306a\u3044\u3067\u3057\u3087\u3046\u3002<\/p>\n\n\n\n<p>\u4e0a\u56f3\u306e\u3088\u3046\u306b\u30012\u6b21\u95a2\u6570\u3068x\u8ef8\u304c2\u70b9\u3067\u4ea4\u308f\u308b\u72b6\u614b\u3092<span class=\"huto\">\u300c\u7570\u306a\u308b2\u3064\u306e\u5b9f\u6570\u89e3\u3092\u3082\u3064\u300d<\/span>\u3068\u3044\u3044\u307e\u3059\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"mondai\">\u5224\u5225\u5f0fD\u306e\u516c\u5f0f\u3092\u7528\u3044\u305f\u7df4\u7fd2\u554f\u984c<\/h2>\n\n\n\n<p>2\u6b21\u95a2\u6570\u306e\u5206\u91ce\u3067\u5224\u5225\u5f0fD\u3092\u4f7f\u3063\u305f\u7df4\u7fd2\u554f\u984c\u306b\u6311\u6226\u3057\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n\n\n\n<div class=\"wp-block-group is-style-bg_stripe\"><div class=\"wp-block-group__inner-container is-layout-constrained wp-block-group-is-layout-constrained\">\n<ul class=\"wp-block-list\">\n<li><a href=\"#mondai1\">\u7df4\u7fd2\u554f\u984c1<\/a><\/li>\n\n\n\n<li><a href=\"#mondai2\">\u7df4\u7fd2\u554f\u984c2<\/a><\/li>\n\n\n\n<li><a href=\"#mondai3\">\u7df4\u7fd2\u554f\u984c3<\/a><\/li>\n<\/ul>\n<\/div><\/div>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"mondai1\">2\u6b21\u65b9\u7a0b\u5f0f\u306e\u5b9f\u6570\u89e3\u306e\u500b\u6570<\/h3>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"682\" height=\"116\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u65b9\u7a0b\u5f0f\u306e\u5224\u5225\u5f0f\u300a\u4f8b\u984c1\u300b.png\" alt=\"2\u6b21\u65b9\u7a0b\u5f0f\u306e\u5224\u5225\u5f0f\u300a\u4f8b\u984c1\u300b\" class=\"wp-image-10366\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u65b9\u7a0b\u5f0f\u306e\u5224\u5225\u5f0f\u300a\u4f8b\u984c1\u300b.png 682w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u65b9\u7a0b\u5f0f\u306e\u5224\u5225\u5f0f\u300a\u4f8b\u984c1\u300b-300x51.png 300w\" sizes=\"auto, (max-width: 682px) 100vw, 682px\" \/><\/figure>\n<\/div>\n\n\n<p>(1)\u3000\\(a=1,b=-4,c=5\\)\u3068\u3057\u3066\u3001\u5224\u5225\u5f0fD\u306e\u7b26\u53f7\u3092\u6c42\u3081\u307e\u3059\u3002<\/p>\n\n\n\n<p>\\begin{eqnarray}<br>D&amp;=&amp;b^{2}-4ac\\<br>&amp;=&amp;(-4)^{2}-4 \\cdot 1 \\cdot 5\\<br>&amp;=&amp;16-20\\<br>&amp;=&amp;-4&lt;0<br>\\end{eqnarray}<\/p>\n\n\n\n<p>\u3057\u305f\u304c\u3063\u3066\u3001\u5b9f\u6570\u89e3\u3092\u3082\u305f\u306a\u3044\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"mondai2\">\u6761\u4ef6\u3092\u6e80\u305f\u3059\\(m\\)\u306e\u7bc4\u56f2<\/h3>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"685\" height=\"119\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u65b9\u7a0b\u5f0f\u306e\u5224\u5225\u5f0f\u300a\u4f8b\u984c2\u300b.png\" alt=\"2\u6b21\u65b9\u7a0b\u5f0f\u306e\u5224\u5225\u5f0f\u300a\u4f8b\u984c2\u300b\" class=\"wp-image-10367\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u65b9\u7a0b\u5f0f\u306e\u5224\u5225\u5f0f\u300a\u4f8b\u984c2\u300b.png 685w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u65b9\u7a0b\u5f0f\u306e\u5224\u5225\u5f0f\u300a\u4f8b\u984c2\u300b-300x52.png 300w\" sizes=\"auto, (max-width: 685px) 100vw, 685px\" \/><\/figure>\n<\/div>\n\n\n<p>(1)\u3000\\(a=1,b=5,c=m\\)\u3068\u3057\u3066\u3001\u5224\u5225\u5f0fD\u306e\u7b26\u53f7\u3092\u6c42\u3081\u308b\u3002<\/p>\n\n\n\n<p>\\begin{eqnarray}<br>D&amp;=&amp;b^{2}-4ac\\<br>&amp;=&amp;5^{2}-4 \\cdot 1 \\cdot m\\<br>&amp;=&amp;25-4m<br>\\end{eqnarray}<\/p>\n\n\n\n<p>\u4e0e\u5f0f\u304c\u7570\u306a\u308b2\u3064\u306e\u5b9f\u6570\u89e3\u3092\u3082\u3064\u305f\u3081\u306b\u306f\u3001\\(D&gt;0\\)\u3067\u3042\u308c\u3070\u3088\u3044\u3002<\/p>\n\n\n\n<p>\u3086\u3048\u306b\u3001<\/p>\n\n\n\n<p>\\begin{eqnarray}<br>25-4m&amp;&gt;&amp;0\\<br>4m&amp;&lt;&amp;25\\<br>m&amp;&lt;&amp;\\frac{25}{4}<br>\\end{eqnarray}<\/p>\n\n\n\n<p>\u3057\u305f\u304c\u3063\u3066\u3001\u6c42\u3081\u308b\u7bc4\u56f2\u306f\\(m&lt; \\dfrac{25}{4}\\)<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"mondai3\">2\u6b21\u95a2\u6570\u3068x\u8ef8\u306e\u5171\u6709\u70b9\u306e\u500b\u6570<\/h3>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"680\" height=\"119\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u65b9\u7a0b\u5f0f\u306e\u5224\u5225\u5f0f\u300a\u4f8b\u984c3\u300b.png\" alt=\"2\u6b21\u65b9\u7a0b\u5f0f\u306e\u5224\u5225\u5f0f\u300a\u4f8b\u984c3\u300b\" class=\"wp-image-10368\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u65b9\u7a0b\u5f0f\u306e\u5224\u5225\u5f0f\u300a\u4f8b\u984c3\u300b.png 680w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u65b9\u7a0b\u5f0f\u306e\u5224\u5225\u5f0f\u300a\u4f8b\u984c3\u300b-300x53.png 300w\" sizes=\"auto, (max-width: 680px) 100vw, 680px\" \/><\/figure>\n<\/div>\n\n\n<p>(1)\u3000\\(y=x^{2}-3x+1\\)\u306b\u3064\u3044\u3066<\/p>\n\n\n\n<p>\\begin{eqnarray}<br>D&amp;=&amp;(-3)^{2}-4 \\cdot 1 \\cdot 1\\<br>&amp;=&amp;9-4\\<br>&amp;=&amp;5&gt;0<br>\\end{eqnarray}<\/p>\n\n\n\n<p>\u3088\u3063\u3066\u3001\u5171\u6709\u70b9\u306e\u500b\u6570\u306f2\u500b<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u5224\u5225\u5f0fD\u3068\u89e3\u306e\u516c\u5f0f\u3092\u4f7f\u3044\u65b9\u306e\u9055\u3044<\/h2>\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"1200\" height=\"655\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2026\/02\/discriminant-ill_1.webp\" alt=\"\u5224\u5225\u5f0fD\uff08\u500b\u6570\u306e\u5224\u5b9a\uff09\u3068\u89e3\u306e\u516c\u5f0f\uff08\u5024\u306e\u7b97\u51fa\uff09\u306e\u4f7f\u3044\u5206\u3051\u6bd4\u8f03\u8868\" class=\"wp-image-21575\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2026\/02\/discriminant-ill_1.webp 1200w, https:\/\/math-travel.jp\/wp-content\/uploads\/2026\/02\/discriminant-ill_1-768x419.webp 768w\" sizes=\"(max-width: 1200px) 100vw, 1200px\" \/><\/figure>\n\n\n\n\n\n<p>\u5224\u5225\u5f0fD\u3068\u6df7\u5408\u3055\u308c\u3084\u3059\u3044\u306e\u304c\u3001\u4e2d\u5b66\u6821\u3067\u7fd2\u3063\u305f\u300c\u89e3\u306e\u516c\u5f0f\u300d\u3067\u3059\u3002<\/p>\n\n\n\n<p>\u5224\u5225\u5f0fD\u3068\u89e3\u306e\u516c\u5f0f\u306f\u3069\u3061\u3089\u30822\u6b21\u95a2\u6570\u306b\u304a\u3044\u3066\u6b20\u304b\u305b\u306a\u3044\u516c\u5f0f\u306a\u306e\u3067\u3001\u78ba\u5b9f\u306b\u7fd2\u5f97\u3057\u307e\u3057\u3087\u3046\u3002<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"722\" height=\"197\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u3068\u89e3\u306e\u516c\u5f0f.png\" alt=\"\u5224\u5225\u5f0f\u3068\u89e3\u306e\u516c\u5f0f\" class=\"wp-image-10360\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u3068\u89e3\u306e\u516c\u5f0f.png 722w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u3068\u89e3\u306e\u516c\u5f0f-300x82.png 300w\" sizes=\"auto, (max-width: 722px) 100vw, 722px\" \/><\/figure>\n<\/div>\n\n\n<p>\u3057\u304b\u3057\u3001\u305d\u308c\u305e\u308c\u306e\u4f7f\u3044\u65b9\u306f\u660e\u78ba\u306b\u7570\u306a\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<p>\u300c\u5b9f\u6570\u89e3\u304c\u3044\u304f\u3064\u3042\u308b\u306e\u304b\u300d\u300c\u5171\u6709\u70b9\u304c\u3044\u304f\u3064\u3042\u308b\u306e\u304b\u300d\u3068\u3044\u3063\u305f\u3001\u89e3\u306e\u500b\u6570\u304c\u5206\u304b\u308c\u3070\u826f\u3044\u554f\u984c\u306b\u5224\u5225\u5f0fD\u3092\u4f7f\u3044\u307e\u3059\u3002<\/p>\n\n\n\n<p>\u3061\u306a\u307f\u306b\u3001\u5224\u5225\u5f0f\u3067\u306f\u89e3\u306e\u500b\u6570\u306f\u5206\u304b\u308a\u307e\u3059\u304c\u3001\u5177\u4f53\u7684\u306ax\u5ea7\u6a19\u306e\u5024\u307e\u3067\u306f\u5206\u304b\u308a\u307e\u305b\u3093\u3002<\/p>\n\n\n\n<p>\u4e00\u65b9\u3067\u3001\u300c\u89e3\u306e\u516c\u5f0f\u300d\u306f\u5224\u5225\u5f0f\u3088\u308a\u3082\u5f37\u529b\u3067\u3059\u3002<\/p>\n\n\n\n<p>\u89e3\u306e\u516c\u5f0f\u3092\u4f7f\u3046\u3053\u3068\u3067\u30012\u6b21\u65b9\u7a0b\u5f0f\u306e\u89e3\u307e\u3067\u5206\u304b\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<p>\u3064\u307e\u308a\u3001\u5224\u5225\u5f0fD\u3068\u89e3\u306e\u516c\u5f0f\u306f\u4ee5\u4e0b\u306e\u3088\u3046\u306b\u4f7f\u3044\u5206\u3051\u307e\u3057\u3087\u3046\u3002<\/p>\n\n\n\n<div class=\"wp-block-group is-style-bg_stripe\"><div class=\"wp-block-group__inner-container is-layout-constrained wp-block-group-is-layout-constrained\">\n<ul class=\"wp-block-list\">\n<li>\u5b9f\u6570\u89e3\u306e\u500b\u6570\u304c\u77e5\u308a\u305f\u3044\u306a\u3089\u21d2\u5224\u5225\u5f0fD<\/li>\n\n\n\n<li>2\u6b21\u65b9\u7a0b\u5f0f\u306e\u89e3\u3092\u6c42\u3081\u305f\u3044\u306a\u3089\u21d2\u89e3\u306e\u516c\u5f0f<\/li>\n<\/ul>\n<\/div><\/div>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"naze\">\u306a\u305c\u5224\u5225\u5f0fD\u306e\u7b26\u53f7\u3067\u89e3\u306e\u500b\u6570\u304c\u5206\u304b\u308b\uff1f<\/h2>\n\n\n<div class=\"swell-block-balloon\"><div class=\"c-balloon -bln-left\" data-col=\"gray\"><div class=\"c-balloon__icon -circle\"><img decoding=\"async\" loading=\"lazy\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2024\/05\/math-travel-hukidashi5-150x150.webp\" alt=\"\" class=\"c-balloon__iconImg\" width=\"80px\" height=\"80px\"><span class=\"c-balloon__iconName\">\u9ad8\u6821\u751f<\/span><\/div><div class=\"c-balloon__body -speaking -border-on\"><div class=\"c-balloon__text\">\n<p>\u306a\u3093\u3067\u5224\u5225\u5f0f\u306e\u7b26\u53f7\u304b\u3089\u89e3\u306e\u500b\u6570\u304c\u5206\u304b\u308b\u306e\u3067\u3059\u304b\uff1f<\/p>\n<span class=\"c-balloon__shapes\"><span class=\"c-balloon__before\"><\/span><span class=\"c-balloon__after\"><\/span><\/span><\/div><\/div><\/div><\/div>\n\n\n<p>\u305d\u3093\u306a\u30ae\u30e2\u30f3\u306e\u58f0\u304c\u805e\u3053\u3048\u3066\u304d\u305d\u3046\u306a\u306e\u3067\u3001\u306a\u305c\u5224\u5225\u5f0fD\u3067\u5b9f\u6570\u89e3\u306e\u500b\u6570\u304c\u5206\u304b\u308b\u306e\u304b\u3092\u89e3\u8aac\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<p>\u307e\u305a\u3001\u5224\u5225\u5f0fD\u306e\u516c\u5f0f\u306f\u4ee5\u4e0b\u306e\u6570\u5f0f\u3067\u3057\u305f\u306d\u3002<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"542\" height=\"162\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u306e\u516c\u5f0f-1.png\" alt=\"\u5224\u5225\u5f0f\u306e\u516c\u5f0f\" class=\"wp-image-7231\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u306e\u516c\u5f0f-1.png 542w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u306e\u516c\u5f0f-1-300x90.png 300w\" sizes=\"auto, (max-width: 542px) 100vw, 542px\" \/><\/figure>\n<\/div>\n\n\n<p>\\(b^{2}-4ac\\)\u3063\u3066\u3069\u3053\u304b\u3067\u898b\u305f\u3053\u3068\u304c\u3042\u308b\u5f62\u3092\u3057\u3066\u3044\u307e\u305b\u3093\u304b\uff1f<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"703\" height=\"235\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f.jpg\" alt=\"\u89e3\u306e\u516c\u5f0f\" class=\"wp-image-970\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f.jpg 703w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f-300x100.jpg 300w\" sizes=\"auto, (max-width: 703px) 100vw, 703px\" \/><\/figure>\n<\/div>\n\n\n<p>\u305d\u3046\u3067\u3059\u3001\u5224\u5225\u5f0fD\u306f\u89e3\u306e\u516c\u5f0f\u306e\u3053\u306e\u90e8\u5206\u3068\u540c\u3058\u5f62\u3092\u3057\u3066\u3044\u308b\u306e\u3067\u3059\uff01<br>\u3064\u307e\u308a\u3001D\u306e\u7b26\u53f7\u306b\u3088\u3063\u3066\u4ee5\u4e0b\u306e3\u30d1\u30bf\u30fc\u30f3\u306b\u5206\u3051\u3066\u8003\u3048\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\\(D&gt;0\\)\u306e\u3068\u304d<\/h3>\n\n\n\n<p>\\(D&gt;0\\)\u306e\u3068\u304d\u3001\u89e3\u306e\u516c\u5f0f\u306b\u304a\u3051\u308b\u30eb\u30fc\u30c8\u90e8\u5206\u304c\u6b63\u306e\u6570\u306b\u306a\u308b\u3053\u3068\u3092\u8868\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<p>\u3064\u307e\u308a\u3001\u4e8c\u6b21\u65b9\u7a0b\u5f0f\u3092\u6e80\u305f\u3059\u89e3\u304c2\u3064\u3042\u308b\u3053\u3068\u3092\u6307\u3057\u307e\u3059\u3002<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"534\" height=\"279\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0fD1.jpg\" alt=\"D\u304c\u6b63\u306e\u3068\u304d\" class=\"wp-image-965\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0fD1.jpg 534w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0fD1-300x157.jpg 300w\" sizes=\"auto, (max-width: 534px) 100vw, 534px\" \/><\/figure>\n<\/div>\n\n\n<p>\u3053\u306e\u3053\u3068\u304b\u3089\u3001D&gt;0\u306e\u3068\u304d\u4e8c\u6b21\u65b9\u7a0b\u5f0f\u304c2\u3064\u306e\u5b9f\u6570\u89e3\u3092\u3082\u3064\u3053\u3068\u304c\u5206\u304b\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\\(D=0\\)\u306e\u3068\u304d<\/h3>\n\n\n\n<p>\\(D=0\\)\u306e\u3068\u304d\u3001\u89e3\u306e\u516c\u5f0f\u306b\u304a\u3051\u308b\u30eb\u30fc\u30c8\u306e\u90e8\u5206\u304c\\(b^{2}-4ac=0\\)\u3067\u3059\u306d\u3002<\/p>\n\n\n\n<p>\u3053\u308c\u306f\u4e8c\u6b21\u65b9\u7a0b\u5f0f\u3092\u6e80\u305f\u3059\u89e3\u304c1\u3064\u3057\u304b\u306a\u3044\u3053\u3068\u3092\u6307\u3057\u307e\u3059\u3002<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"530\" height=\"161\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0fD0.jpg\" alt=\"D\u304c0\u306e\u3068\u304d\" class=\"wp-image-973\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0fD0.jpg 530w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0fD0-300x91.jpg 300w\" sizes=\"auto, (max-width: 530px) 100vw, 530px\" \/><\/figure>\n<\/div>\n\n\n<p>\u3057\u305f\u304c\u3063\u3066\u3001D=0\u306e\u3068\u304d\u4e8c\u6b21\u65b9\u7a0b\u5f0f\u306f\u5b9f\u6570\u89e3\u30921\u3064\u3082\u3064\u3053\u3068\u304c\u5206\u304b\u308a\u307e\u3057\u305f\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\\(D&lt;0\\)\u306e\u3068\u304d<\/h3>\n\n\n\n<p>\\(D&lt;0\\)\u306e\u3068\u304d\u3001\u89e3\u306e\u516c\u5f0f\u306b\u304a\u3051\u308b\u30eb\u30fc\u30c8\u90e8\u5206\u306e\u4e2d\u8eab\u304c\u30de\u30a4\u30ca\u30b9\u306b\u306a\u3063\u3066\u3057\u307e\u3044\u307e\u3059\u3002<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"405\" height=\"135\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f-D-e1622697993655.jpg\" alt=\"D\u304c\u8ca0\u306e\u3068\u304d\" class=\"wp-image-972\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f-D-e1622697993655.jpg 405w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u89e3\u306e\u516c\u5f0f-D-e1622697993655-300x100.jpg 300w\" sizes=\"auto, (max-width: 405px) 100vw, 405px\" \/><\/figure>\n<\/div>\n\n\n<p>\u6570\u5b66\u2160\u306e\u6bb5\u968e\u3067\u306f\u30eb\u30fc\u30c8\u306e\u4e2d\u8eab\u304c\u6b63\u306e\u6570\u3067\u306a\u3051\u308c\u3070\u306a\u3089\u306a\u3044\u305f\u3081\u3001\\(D&lt;0\\)\u306e\u3068\u304d\\(x\\)\u306f\u5b9f\u6570\u89e3\u3092\u6301\u305f\u306a\u3044\u306e\u3067\u3059\u3002<\/p>\n\n\n\n<p>\u3053\u308c\u306f\u4f59\u8ac7\u3067\u3059\u304c\u3001\u6570\u2161\u3067\u306f\u30eb\u30fc\u30c8\u306e\u4e2d\u304c\u8ca0\u306e\u6570\u306b\u306a\u308b\u3053\u3068\u304c\u3042\u308a\u3001\u300c\u865a\u6570\u300d\u3068\u547c\u3070\u308c\u308b\u5358\u5143\u306b\u7e4b\u304c\u3063\u3066\u3044\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<p>\uff1e\uff1e\u5b9f\u6570\u3068\u306f\uff1f\u5b9f\u6570\u306b\u542b\u307e\u308c\u308b\u3082\u306e\uff06\u5b9f\u6570\u3067\u306a\u3044\u3082\u306e\u3092\u5177\u4f53\u4f8b\u3067\u89e3\u8aac<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"d\/4\">\u5224\u5225\u5f0fD\/4\u3092\u6d3b\u7528\u3057\u3088\u3046<\/h2>\n\n\n\n<p>\u5224\u5225\u5f0fD\u3092\u5c11\u3057\u5fdc\u7528\u3057\u305f\u3082\u306e\u3067\u3001\\(\\displaystyle \\frac{D}{4}\\)\u3068\u3044\u3046\u3082\u306e\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<p>\\(\\displaystyle \\frac{D}{4}\\)\u306f\u4e0e\u3048\u3089\u308c\u305f\u4e8c\u6b21\u65b9\u7a0b\u5f0f\\(ax^{2}+bx+c=0\\)\u306e<span class=\"yellow-hoso\">\\(b\\)\u304c\u5076\u6570\u306e\u3068\u304d\u306b\u3060\u3051\u4f7f\u3048\u308b\u516c\u5f0f<\/span>\u3067\u3059\u3002<\/p>\n\n\n\n<div class=\"swell-block-capbox cap_box is-style-onborder_ttl2\"><div class=\"cap_box_ttl\"><span>\u5224\u5225\u5f0fD\/4<\/span><\/div><div class=\"cap_box_content\">\n<p>\\(y=ax^{2}+bx+c\\)\u306b\u304a\u3044\u3066\u3001\\(b\\)\u304c\u5076\u6570\u306e\u3068\u304d\\(\\displaystyle b&#8217;=\\frac{b}{2}\\)\u3068\u3059\u308b\u3068<\/p>\n\n\n\n<p>\\[\\displaystyle \\frac{D}{4}=b&#8217;^{2}-ac\\]<\/p>\n<\/div><\/div>\n\n\n\n<p>\u4f8b\u3068\u3057\u3066\u3001\u4e8c\u6b21\u65b9\u7a0b\u5f0f\\(x^{2}+6x+3=0\\)\u306e\u89e3\u306e\u500b\u6570\u3092\u6c42\u3081\u307e\u3057\u3087\u3046\u3002<\/p>\n\n\n\n<p>\\(x\\)\u306e\u4fc2\u6570\u304c\\(6\\)\u3067\u5076\u6570\u306a\u306e\u3067\u3001\u5224\u5225\u5f0f\\(\\displaystyle \\frac{D}{4}\\)\u3092\u4f7f\u3046\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<p>\\(b&#8217;=3\\)\u3068\u3059\u308b\u3068\u3001<\/p>\n\n\n\n<p>\\begin{eqnarray}<br>\\frac{D}{4}&amp;=&amp;b&#8217;^{2}-ac\\\\<br>&amp;=&amp;3^{2}-1 \\cdot 3\\\\<br>&amp;=&amp;6<br>\\end{eqnarray}<\/p>\n\n\n\n<p>\\(\\displaystyle \\frac{D}{4}&gt;0\\)\u3088\u308a\u3001\u4e0e\u3048\u3089\u308c\u305f\u4e8c\u6b21\u65b9\u7a0b\u5f0f\u306f\u7570\u306a\u308b2\u3064\u306e\u5b9f\u6570\u89e3\u3092\u3082\u3064\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u306a\u3093\u3067\u5224\u5225\u5f0f\u306e\u516c\u5f0f\u306fD\u306a\u306e\uff1f<\/h2>\n\n\n\n<p>\u3053\u3053\u3067\u5c11\u3057\u4f59\u8ac7\u306a\u306e\u3067\u3059\u304c\u3001\u300c\u306a\u305c\u5224\u5225\u5f0f\u306e\u8a18\u53f7\u306fD\u306a\u306e\u3067\u3057\u3087\u3046\u304b\u300d\u3002<br>\u305d\u308c\u306b\u306f\u3061\u3083\u3093\u3068\u3057\u305f\u7531\u6765\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n\n\n<div class=\"swell-block-balloon\"><div class=\"c-balloon -bln-left\" data-col=\"gray\"><div class=\"c-balloon__icon -circle\"><img decoding=\"async\" loading=\"lazy\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2024\/05\/math-travel-hukidashi5-150x150.webp\" alt=\"\" class=\"c-balloon__iconImg\" width=\"80px\" height=\"80px\"><span class=\"c-balloon__iconName\">\u9ad8\u6821\u751f<\/span><\/div><div class=\"c-balloon__body -speaking -border-on\"><div class=\"c-balloon__text\">\n<p>\u306a\u3093\u3067\u5224\u5225\u5f0f\u306e\u8a18\u53f7\u306f&#8221;D&#8221;\u306a\u3093\u3060\u308d\u3046\uff1f<\/p>\n<span class=\"c-balloon__shapes\"><span class=\"c-balloon__before\"><\/span><span class=\"c-balloon__after\"><\/span><\/span><\/div><\/div><\/div><\/div>\n\n\n<p>D\u306f\u82f1\u8a9e\u306e\u7565\u79f0\u3067\u82f1\u5358\u8a9e\u306e<span class=\"huto\">\u300cdiscriminant\u300d\uff08\u65e5\u672c\u8a9e\u8a33\uff1a\u5224\u5225\u3001\u5dee\u5225\u3001\u533a\u5225\uff09<\/span>\u304c\u7531\u6765\u306b\u306a\u3063\u3066\u3044\u307e\u3059\u3002<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"609\" height=\"88\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u304cD\u306e\u7406\u7531.png\" alt=\"\u5224\u5225\u5f0f\u304cD\u306e\u7406\u7531\" class=\"wp-image-10374\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u304cD\u306e\u7406\u7531.png 609w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/\u5224\u5225\u5f0f\u304cD\u306e\u7406\u7531-300x43.png 300w\" sizes=\"auto, (max-width: 609px) 100vw, 609px\" \/><\/figure>\n<\/div>\n\n\n<p>\u4f55\u6c17\u306a\u304f\u4f7f\u3063\u3066\u3044\u308b\u6570\u5b66\u306e\u8a18\u53f7\u306b\u306f\u3061\u3083\u3093\u3068\u610f\u5473\u304c\u3042\u308b\u306e\u3067\u3001\u305d\u3053\u3092\u6c17\u306b\u3057\u3066\u307f\u3066\u3082\u9762\u767d\u3044\u3067\u3059\u306d\uff01<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"matome\">\u5224\u5225\u5f0fD\u306e\u516c\u5f0f\u307e\u3068\u3081<\/h2>\n\n\n\n<p>\u4eca\u56de\u306f\u4e8c\u6b21\u65b9\u7a0b\u5f0f\u306e\u5224\u5225\u5f0f\u306b\u3064\u3044\u3066\u307e\u3068\u3081\u307e\u3057\u305f\u3002<\/p>\n\n\n\n<p>\u5224\u5225\u5f0fD<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"756\" height=\"386\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u95a2\u6570\u306e\u5224\u5225\u5f0f.png\" alt=\"2\u6b21\u95a2\u6570\u306e\u5224\u5225\u5f0f\" class=\"wp-image-5603\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u95a2\u6570\u306e\u5224\u5225\u5f0f.png 756w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u95a2\u6570\u306e\u5224\u5225\u5f0f-300x153.png 300w\" sizes=\"auto, (max-width: 756px) 100vw, 756px\" \/><\/figure>\n<\/div>\n\n\n<p>\u5224\u5225\u5f0fD\u3068x\u8ef8\u3068\u306e\u5171\u6709\u70b9\u306e\u500b\u6570<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter\"><img loading=\"lazy\" decoding=\"async\" width=\"746\" height=\"256\" src=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u65b9\u7a0b\u5f0f\u306e\u89e3.png\" alt=\"2\u6b21\u65b9\u7a0b\u5f0f\u306e\u89e3\" class=\"wp-image-5604\" srcset=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u65b9\u7a0b\u5f0f\u306e\u89e3.png 746w, https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/2\u6b21\u65b9\u7a0b\u5f0f\u306e\u89e3-300x103.png 300w\" sizes=\"auto, (max-width: 746px) 100vw, 746px\" \/><\/figure>\n<\/div>\n\n\n<p>\u5224\u5225\u5f0fD\u306f\u91cd\u8981\u306a\u516c\u5f0f\u3067\u3059\u3002\u306a\u306e\u3067\u3001\u5fc5\u305a\u62bc\u3055\u3048\u3066\u304a\u304d\u307e\u3057\u3087\u3046\uff01<\/p>\n\n\n\n<div class=\"wp-block-group has-border -border02 is-style-bg_grid\"><div class=\"wp-block-group__inner-container is-layout-constrained wp-block-group-is-layout-constrained\">\n<div id=\"kv\">\n        <p>\\(ax^{2}+bx+c=0\\) \u306e\u4e8c\u6b21\u65b9\u7a0b\u5f0f\u306e\u89e3\u306e\u500b\u6570\u3092\u5224\u5225\u5f0f\u3092\u57fa\u306b\u5c0e\u51fa\u3057\u307e\u3059\u3002<br>\n          \u4fc2\u6570\u3092\u5165\u529b\u5f8c\u3001\u7b97\u51fa\u30dc\u30bf\u30f3\u3092\u30af\u30ea\u30c3\u30af\u3057\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n      <\/div>\n      <div class=\"input-coefficient\">\n        <div class=\"number-item\">\n          <label>a:<\/label>\n          <input type=\"number\" name=\"a1\" class=\"a1\">\n        <\/div>\n        <div class=\"number-item\">\n          <label>b:<\/label>\n          <input type=\"number\" name=\"a2\" class=\"a2\">\n        <\/div>\n        <div class=\"number-item\">\n          <label>c:<\/label>\n          <input type=\"number\" name=\"a3\" class=\"a3\">\n        <\/div>\n      <\/div>\n      <div class=\"output\">\n        <p><span id=\"origin-formula\"><\/span> \u306e\u4e8c\u6b21\u65b9\u7a0b\u5f0f\u306e\u89e3\u306e\u500b\u6570\u306f\u3001<br>\\(D=b^{2}-4ac=\\)<span id=\"discriminant\"><\/span>\u3088\u308a<br><span id=\"result\" class=\"bold\"><\/span>\u3092\u6301\u3064\u3002<\/p>\n      <\/div>\n      <div class=\"output-error\">\n        <p>a \u306e\u5024\u306f0\u4ee5\u5916\u3092\u5165\u529b\u3057\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n      <\/div>\n      <div class=\"btn\">\n        <input type=\"button\" value=\"\u7b97\u51fa\" id=\"cal-btn\">\n        <input type=\"button\" value=\"\u30ea\u30bb\u30c3\u30c8\" id=\"reset-btn\">\n      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\u9ad8\u6821\u6570\u5b66\u306b\u304a\u3044\u3066\u3001\u5224\u5225\u5f0fD\u306f\u975e\u5e38\u306b\u91cd\u8981\u306a\u516c\u5f0f\u306e1\u3064\u3067\u3059\u3002 \u5224\u5225\u5f0fD\u3092\u6c42\u3081\u308b\u516c\u5f0f\u306f\u4ee5\u4e0b\u306e\u901a\u308a\u3067\u3059\u3002 \u5224\u5225 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":21573,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"swell_btn_cv_data":"","footnotes":""},"categories":[21,222],"tags":[22,10,11],"class_list":["post-953","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-nizikansuu","category-math-1","tag-22","tag-a","tag-11"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.8 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ 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content=\"2026-02-28T06:37:05+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/math-travel.jp\/wp-content\/uploads\/2020\/04\/3.png\" \/>\n\t<meta property=\"og:image:width\" content=\"1920\" \/>\n\t<meta property=\"og:image:height\" content=\"1080\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"author\" content=\"\u3086\u3046\u3084\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@https:\/\/twitter.com\/mathtora\" \/>\n<meta name=\"twitter:label1\" content=\"\u57f7\u7b46\u8005\" \/>\n\t<meta name=\"twitter:data1\" content=\"\u3086\u3046\u3084\" \/>\n\t<meta name=\"twitter:label2\" content=\"\u63a8\u5b9a\u8aad\u307f\u53d6\u308a\u6642\u9593\" \/>\n\t<meta name=\"twitter:data2\" content=\"14\u5206\" \/>\n<script type=\"application\/ld+json\" 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