2a/(a²-4)+1/(2-a)
=2a/[(a-2)(a+2)]-1/(a-2)
=[2a-(a+2)]/[(a-2)(a+2)]
=1/(a-2)
x/(x-y)-2y/(x-y)）•xy/(x-2y)+（1/x+1/y)
=(x-2y)/(x-y) •xy/(x-2y)+(1/x+1/y)
=xy/(x-y)+(x-y)/xy
=(x+y)/(x-y)
3/(2x-2)+1/(1-x)+3
=(3-2)/(2(x-1))+3
=1/(2x-1)+3
(1-x)/(x-2)=1/(2-x)-2
=有问题