Упростите выражение: xy(x+y)-(x^2+y^2)(2x-y).

\[\text{xy}(x + y) - \left( x^{2} + y^{2} \right)(2x - y) =\]

\[= x^{2}y + xy^{2} - \left( 2x^{3} - x^{2}y + 2xy^{2} - y^{3} \right) =\]

\[= x^{2}y + xy^{2} - 2x^{3} + x^{2}y - 2xy^{2} + y^{3} =\]

\[= - 2x^{3} + 2x^{2}y - xy^{2} + y^{3}\text{.\ }\]