(a-b)^2/ab-(a^2-b^2)/ab

问题描述:

(a-b)^2/ab-(a^2-b^2)/ab

=[(a-b)^2-(a^2-b^2)]/ab
=(a^2-2ab+b^2-a^2+b^2)/ab
=(-2ab+2b^2)/ab
=(2b-2a)/a