7y（x-3y）^2-2(3y-x)^3.帮忙做一下,偶不是很确定我的答案是对的

化简3(x-y)-7(x--y)+2(y-x) 2（x-y）²-3(x-y)(-y-x) x(x-y)2-(y-x)3 [(3x+y)(x-y)-(2x+3y)(x-y)]*(x-y) 计算：x+2y/x-y+2x/y-x-3y/x-y 化简:(x-3y)(x+y)-(x-2y)(x+2y)-(x-y)平方 3x+y=2 -y/x+y=123x+y=2 （-y/x）+y=12 （-7x^2-8y^2）*(-x^2+3y^2) (3x-2y)(y-3x)-(2x-y)(3x+y) 已知（x+y）2 =2,(x-y)3 =3,求(x+y)7(x-y)2(x+y)3(y-x)4 的值 (-3x+7y)(-7y-3x)-(x-3y)(2x+3y) [2/3x-2/x+y(x+y/3x-x-y)]/x-y/x 化简：{2/3x-2/(x+y)[(x+y)/3x-x-y]}/(x+y)/x 计算2/3x-2/x+y(x+y/3x-x-y)/x-y/x 已知方程组{(X+Y)-3(X-Y)=7,2(X+Y)+(X-Y）=-7}则(X+Y)(X-Y)= 18(x+y)^8(x-y)^7÷[3(x+y)^3(x-y)^3]^2 化简3x-2/(x+y)[(x+y)/3x-x-y]÷(x-y)/x 3(x-y)^2-7(x-y)+8(y-x)^2+6(y-x)合并同类项. 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于