Помогите с 3 заданием пожалуйста!!

y^2/x^2-xy:(y/x+y-2xy/x^2-y^2)=
y^2/x(x-y):(y/x+y-2xy/(x-y)(x+y))=
y^2/x(x-y):(xy-x^2-2xy/(x-y)(x+y))=
y^2/x(x-y)*(x-y)(x+y)/-x^2-xy=-y^2/x^2

Решение
1) (y /(x + y) - (2xy) / [(x - y)*(x + y)] = [y*(x - y) - 2xy] / ([x - y)*(x + y)] = 
= - (xy + y²) / [(x - y)*(x + y)] = - [y*(x + y)] / [(x - y)*(x + y)] = 
= - y / (x - y)
2) y² / [x*(x - y)]  : [ - y / (x - y)] = [y² * (x - y)] / [ - y * x*(x - y)] = - y / x