先化简,再求值:(1-x/x+2)·(x2-4/x2-2x+1)÷(1/x2-1)其中x2-x=0.

题目

先化简,再求值:(1-x/x+2)·(x2-4/x2-2x+1)÷(1/x2-1)其中x2-x=0.

答案

原式=-(x-1)/(x+2)*(x+2)(x-2)/(x-1)²*(x²-1)
=-(x-2)/(x-1)*(x+1)(x-1)
=-(x-2)(x+1)
=-(x²-x-2)
=-(0-2)
=2