Substitution of variable is a method of solving extreme value and maximum of a function , which can simplify the problem , but is subject to making mistakes , about this discussion is made and a few results are given in the paper 摘要變量代換法是求函數(shù)極值與最值的方法之一,它可使問題簡化,但也容易導(dǎo)致錯誤,本文對此進(jìn)行了探討,并給出了幾個結(jié)論。