(x-2xy)*(-xy+2y*y)-(3x*x-2xy)(x-9xy+6y*y)

(x-2xy)*(-xy+2y*y)-(3x*x-2xy)(x-9xy+6y*y) （xy-x^2)乘以(xy)/(x-y) x^2-xy-6y^2+3xy+y+2 化简：x-y/x+3y÷x^-y^2/x^2+6xy+9y^2-(xy/x+y) （x^2+xy/x-y)/（xy/x-y)计算 1、(-7x^y)(2x^y-3xy^3+xy) 2、((x-y)^6)/((y-x)^3)/(x-y) (x+y-2xy)(x+y-2)+(1-xy)² (x^2-xy)y÷y-x/xy怎么做? 计算3xy[2xy-x(y-2)+x-1] 计算：3xy[2xy-x（y-2）+x] （-3x^y+2xy)-( )=4x^+xy 已知xy/x+y=6,求3x-2xy+3y/-x+3xy-y的值.