推荐回答(3个)
求函数值域方法•常数分离法•不等式法•配方法•逆求法•换元法•判别式法
一、 配方法
通过配方结合函数图像求函数的值域,一般地,对于二次函数 求值域问题可运用配方法.
二、 反函数法
一般地,形如 ,可利用原函数与反函数的定义域和值域之间的互逆关系.
三、 分离常数法
一般地,对于分式函数来说,可以分离一个常数去求函数的值
四、 判别式法
一般地.形如 ,转化为关于y的一元二次方程,利用方程有实数解, 来求y.
五、 换元法
一般地,形如 ,通过换元 (注意此时t的范围)
六、 分类讨论法
通过分类讨论函数定义域x的符号去求值域.
首先先确定函数的定义域
然后分析是个什么样的函数
如果是偶函数 还要求出他的对称轴 再根据定义域确定最大值和最小值
如果是奇函数 就根据定义域的最大小值代入直接求出值域
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