[(x2-2x)/(x2-1)]÷[x-1-(2x-1)/(x+1)],其中x=1/2
问题描述：
[(x2-2x)/(x2-1)]÷[x-1-(2x-1)/(x+1)],其中x=1/2
先化简，再求值
答
原式=(x²-2x)/[(x+1)(x-1)]÷[(x²-1-2x+1)/(x+1)]
=(x²-2x)/[(x+1)(x-1)]·(x+1)/(x²-2x)
=1/(x-1)
把x=1/2代入最后的结果得
原式的值=-2