Question

[（a-2/a²+2a）-（a-1/a²+4a+4）]÷a-4/a+2=

帮忙写出过程，谢谢

Answer 1

原式=[(a-2)/a(a+2)-(a-1)/(a+2)²]×[(a+2)/(a-4)]
={[(a-2)(a+2)-a(a-1)]/a(a+2)²}×[(a+2)/(a-4)]
=[(a²-4-a²+a)/a(a+2)²}×[(a+2)/(a-4)]
=[(a-4)/a(a+2)²}×[(a+2)/(a-4)]
=1/(a²+2a)

Answer 2

(x-y)^7
=[-1*(y-x)]^7
=(-1)^y*(y-x)^7
=-(y-x)^7

所以原式=-(y-x)^7÷(y-x)^3÷(y-x)^2
=-(y-x)^(7-3-2)
=-(y-x)^2