Помогите пожалуйста!!! во вложении

Решите задачу:

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