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如何轻松找出一个二次函数的最大值或最小值

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抛物线顶点的纵坐标值（一般用k表示），是该二次函数的最大值或最小值。我们学下怎么找它的值吧！

方法 1

方法 1 的 3:

y = ax ² + bx + c 形式

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1
确定你要找的是最大值还是最小值。 只能找其中一个，不能同时找俩。
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方法 2

方法 2 的 3:

y = a(x-h) ² + k 形式

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1
对于y = a(x-h) ² + k ， k 就是顶点的函数最值。
- k 是二次函数的最大值或最小值，根据 a 的正负有所变化。
  
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方法 3

方法 3 的 3:

例子

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小提示

抛物线的对称轴为x = h
-h 是取得最值时的自变量值。

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