(y/x-y + x/x+y) : (1/x^2+1/y^2) - y^4/x^2-y^2Решите подробно, пожалуйста!

$( \frac{y}{x-y} + \frac{x}{x+y} ):( \frac{1}{ x^{2} } + \frac{1}{ y^{2} }) - \frac{y^{4}}{ x^{2} - y^{2} } \\ 1) \frac{y}{x-y} + \frac{x}{x+y} = \frac{y(x+y)+x(x-y)}{ x^{2} - y^{2} } = \frac{xy+y ^{2}+ x^{2} -xy }{ x^{2} - y^{2} } = \frac{ x^{2} + y^{2} }{ x^{2} - y^{2} } \\ 2) \frac{1}{ x^{2} } + \frac{1}{ y^{2} }= \frac{ x^{2} + y^{2} }{ x^{2} y^{2} } \\$

$3)\frac{ x^{2} + y^{2} }{ x^{2} - y^{2} } : \frac{ x^{2} + y^{2} }{ x^{2} y^{2} } = \frac{ x^{2} + y^{2} }{ x^{2} - y^{2} }* \frac{ x^{2} y^{2} }{ x^{2} + y^{2} } = \frac{ x^{2} y^{2} }{ x^{2} - y^{2} } \\ 4)\frac{ x^{2} y^{2} }{ x^{2} - y^{2} } - \frac{y^{4}}{ x^{2} - y^{2} } = \frac{ x^{2} y^{2}-y^{4} }{ x^{2} - y^{2} } = \frac{ y^{2}( x^{2} - y^{2} ) }{ x^{2} - y^{2} } = y^{2} \\$

Ответ: у²