好的
x/(y²-4y+4)=x/(y-2)²=x/(2-y)²=xy/[y(2-y)²]
(x+1)/[y(2-y)]=(x+1)(2-y)/[y(2-y)²]
1/y=(2-y)²/[y(2-y)²]
看明白了吗