-1/2(4xy-8x^2y^2)+1/3(xy-6x^2y^2)化简,谢谢

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 计算3xy[2xy-x(y-2)+x-1] 化简!1、（x^2-xy）+xy+y^2 2、3（x^2-xy）-xy+y^2 [3xy(1-x)-6xy(x-1/2)]*2x*(-xy)平方,x=-1 y=2 ； 3xy平方（-1/3x平方y+4 (x-2xy)*(-xy+2y*y)-(3x*x-2xy)(x-9xy+6y*y) 若x-y=4,xy=1,求(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 已知：x-y=1,xy=-2.求：(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 x-y=1,xy=2.求：(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 .已知:x-y=1,xy=-2.求:(-2xy+2 x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 先化简,再求值：（6x-2y)*3/2xy^2-(xy-3)(xy+1)-(3x-4y)(3x+4y)+(2x-1/2y xy(xy+1)+(xy+3)-2(x+y+2分之一）-(x+y-1)的平方