化简:-(x^2-2xy-y^2)+(5x^2-2xy-3y^2)

（xy-x^2)乘以(xy)/(x-y) (x-2xy)*(-xy+2y*y)-(3x*x-2xy)(x-9xy+6y*y) x^3y(-4y)^2+(-7xy)^2*(-xy)-5xy^3*(-3x)^2 （x^2+xy/x-y)/（xy/x-y)计算 化简：x-y/x+3y÷x^-y^2/x^2+6xy+9y^2-(xy/x+y) x^2-xy-6y^2+3xy+y+2 5x^2y/-1/2xy*3xy^2 化简:-(x^2-2xy-y^2)+(5x^2-2xy-3y^2) 化简 -(x^2-2xy-y^2)+(5x^2-2xy-3y^2) 化简!1、（x^2-xy）+xy+y^2 2、3（x^2-xy）-xy+y^2 5xy^2-[3xy^2-(4xy^2-2x^y)]+x^2y-xy^2如何化简 已知x^2-xy=5,xy-y^2=-3求3(x^2-xy)-xy+y^2