先化简,再求值:(X2次-4/X2次-4X+4减X-2/X+2)乘X-2/X,X=1

问题描述:

先化简,再求值:(X2次-4/X2次-4X+4减X-2/X+2)乘X-2/X,X=1

凑两个完全平方
[X^2-(4/X)^2-4X+4-X-2/X+2]X-2/X
=[X^2-5X-(4/X)^2-2/X+2]X-2/X
=[(X-5/2)^2-(4/X+1/4)^2-25/4+1/16+2]X-2/X
带入X=1
得14