先化简,再求值：已知,化简xy(x+y的平方）-y的平方(xy-x)+2x(x-y的平方),并求它们的值.
x+y=5,2x-y=1 ＝＝> x＝2,y＝3
xy(x+y^2)-y^2(xy-x)+2x(x-y^2)
=x^2y+xy^3-xy^3+xy^2+2x^2-2xy^2
=x^2y+2x^2-xy^2
=12+8-18
=2