(4х²-1)/(у-2ху)=((2х+1)(2х-1)) / (у(1-2х))=((2х+1)(2х-1)) / (-у(2х-1))= - (2х-1)/у
(2z²-8)/(z²-2z)=(2(z-2)(z+2)) / (z(z-2))=(2z+4)/z
(ab²-ac²)/(c²-bc)=(a(b-c)(b+c)) / (c(c-b))=(a(b-c)(b+c)) / (-c(c-b))= - (ab+ac)/c
(x^4 - x²y²)/(ay² -axy)=(x²(x-y)(x+y)) / (ay(y-x))=(x²(x-y)(x+y)) / (-ay(x-y))= - (x²(x+y))/ay