Срочно!!!!!!! Помогите решить примееееррр

[latex] (dfrac{x^2}{y} - 3x - dfrac{y^2}{x} + 3y) cdot dfrac{xy}{x^2 - y^2} = (dfrac{x^3 - y^3}{xy} - 3(x - y)) cdot dfrac{xy}{(x - y)(x + y)} \ \ = dfrac{(x - y)(x^2 + xy + y^2)- 3xy(x - y)}{xy} cdot dfrac{xy}{(x - y)(x + y)} = \ \ = dfrac{(x - y)(x^2 + xy + y^2 - 3xy)xy}{xy(x - y)(x + y)} = \ \ = dfrac{(x - y)^2}{x + y } [/latex]