帮我化简几道分式!

题目

帮我化简几道分式!
2x/x-y =
y^2-4/y+2=
x^2-1/x^2+x=
x^2-6x+9/x^2=9
x^2-16/x^2-8x+16=
2y-xy/x^2-2x=

答案

2-y
y-2
x-1/x
x+3/x-3
x+4/x-4
-y/x