Question

Выражение: (x+y - 4xy/ x+y) · (y-x + 4xy/ y-x)

Answer 1

$(x+y-\frac{ 4xy}{ x+y})\cdot(y-x+\frac{ 4xy}{ y-x})=(\frac{(x+y) ^{2}-4xy }{ x+y})\cdot(\frac{(y+x) ^{2}-4xy}{ y-x})=(\frac{x ^{2}+2xy+y^{2} - 4xy}{ x+y})\cdot(\frac{y^{2}-2xy+x ^{2}+ 4xy}{ y-x})= \\ =(\frac{(x-y) ^{2} }{ x+y})\cdot(\frac{(y+x) ^{2}}{ y-x}=y ^{2} -x ^{2}$