求二次函数解析式的取值范围怎么求(初高中范围)能用 数学二次函数求取值范围
\u600e\u6837\u6c42\u4e8c\u6b21\u51fd\u6570\u7684\u53d6\u503c\u8303\u56f4\u4e5d\u5e74\u7ea7\u6570\u5b66\uff1a\u4e8c\u6b21\u51fd\u6570\u56fe\u8c61\u6c42\u53d6\u503c\u8303\u56f4
\u51fd\u6570\u6027\u8d28\uff1a\u82e5\u51fd\u6570f(x)\u6ee1\u8db3\uff1af(a+x)=f(b-x)\uff0c\u5219f(x)\u5173\u4e8e\u76f4\u7ebfx=(a+b)/2\u5bf9\u79f0\u3002
\u8be5\u9898\uff1af(4+x)=f(-x)\uff0c\u5219f(x)\u7684\u5bf9\u79f0\u8f74\u4e3ax=2\uff1b
f(2)=1,\u8fd9\u5c31\u662ff(x)\u7684\u6700\u4f4e\u70b9\uff1b
\u628af(0)=3\uff0c\u7531\u5bf9\u79f0\u53ef\u5f97f(4)=3\uff1bf(x)\u7684\u6700\u5c0f\u503c\u662f1\uff0c\u6700\u5927\u503c\u662f3\uff1b
\u6240\u4ee5\uff0c\u8981\u4f7f\u5f97f(x)\u5728[0,m]\u4e0a\u6709\u6700\u5c0f\u503c1\uff0c\u5219\u5bf9\u79f0\u8f74x=2\u8981\u5728\u533a\u95f4[0,m]\u5185\uff0c\u4e14m\u4e0d\u80fd\u8d85\u51fa4\uff1b
\u6240\u4ee5\uff1a2\u2266m\u22664\uff1b
\u5e0c\u671b\u80fd\u5e2e\u5230\u4f60\uff0c\u5982\u679c\u4e0d\u61c2\uff0c\u8bf7Hi\u6211\uff0c\u795d\u5b66\u4e60\u8fdb\u6b65\uff01
举个例子,如
f(x)=2x²+3x+5
=2(x²+3/2*x)+5
=2(x²+3/2*x+9/16)-9/8+5
=2(x+3/4)²+31/8
所以f(x)的值域为[31/8,+∞)。
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