（3x-2y+7)(3x-2y-7)=

若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 化简3(x-y)-7(x--y)+2(y-x) 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 7y(x-3y)-2(3y-x)=0 .x=?,y=? 3x+5y-(x+y)=6 2(x+y)-3x=-7 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 x+y=1 5x-2y=8 3x-y=7 2x-y=3x表示y和用y表示x 已知方程组{(X+Y)-3(X-Y)=7,2(X+Y)+(X-Y）=-7}则(X+Y)(X-Y)= 已知实数x.y满足根号(x+y-8)+根号(8-x-y)=根号(3x-y-4)+根号(x-2y+7),求x,y (-3x+7y)(-7y-3x)-(x-3y)(2x+3y) 18(x+y)^8(x-y)^7÷[3(x+y)^3(x-y)^3]^2 3(x-y)^2-7(x-y)+8(y-x)^2+6(y-x)合并同类项. 计算：(x-y)^7÷(y-x)^6+(-x-y)^3÷(x+y)^2 2(y-x)的平方-7(x-y)+6(x-y)-3(y-x)的平方 计算(x-y)^7÷(y-x)^6+9-x-y)^3÷(x+y)^2 化简:3(x-y)²-7(x-y)+ 2(x-y)²+5(x-y) 计算(x^8-x^7y+x^5y^3-x^4y^4+x^3y^5-x^y^7+y^8)(x^2+xy+y^2) 把(x-y)看作一个整体,化解:5(x-y)+2(x-y)-4(x-y)= 3(x-y)把(x-y)看作一个整体,化解:5(x-y)+2(x-y)-4(x-y)=3(x-y)²-4(x-y)+7(x-y)-6(x-y)²=