（1）x²/x-1 -x-1
=x²/(x-1)-(x+1)(x-1)/(x-1)
=[x²-(x+1)(x-1)]/(x-1)
=1/(x-1)
（2）x²+2x/x²-4 - 2/x-2
=x(x+2)/(x+2)(x-2)-2/(x-2)
=x/(x-2)-2/(x-2)
=(x-2)/(x-2)
=1
（3）（x/x+1 - 3x/x-1）÷ x/x²-1
=x/(x+1)× (x+1)(x-1)/x -3x/(x-1)× (x+1)(x-1)/x
=x-1-3x-3
=-2x-4
（4）（1+ 2b/a-b）² · （1- 2b/a+b）²
=(a-b+2b)²/(a-b)² ×(a+b-2b)²/(a+b)²
=(a+b)²/(a-b)² ×(a-b)²/(a+b)²
=1