x的平方-1分之x的平方-2x +1除以x+1分之2x-2

=(x-1)²/(x+1)(x-1)÷2(x-1)/(x+1)
=(x-1)/(x+1)×(x+1)/2(x-1)
=1/2
当x=3、-5、7时它的值都是1/2