3X-2y=9,x-y=7.2X-3y=10.3x-2y=20.4x-y=14,3x+y=7.2\1x-2y=7,2\1-3y=-8.2m+7n=5,3M+n=-2.2u-5v=12,4u+3v=-2.

3(x+y)-2(x-y)=11 4(x+y)+3(x-y)=9 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 (x+y)(x-y)+(x-y)平方-(x-y)(3x-y) 其中x=-2 y=3分之一 (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 (x+y)(2x-3y)=? 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= 已知x-y=3,求[（x+y)(x-y)-(x-y)^2+2y(x-y)]除以的值 已知3x =2y 求x/x+y+y/x-y-y²/x²-y² （x+y-5)*（x+y-5)+（x-y+3)=0 x*x-y*y 已知:3x-5y=0,求x/y,x-y/y,x-y/x 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 推倒公式:(x+y)(x*x-3x+y*y)=x*x*x+y*y*y怎么做. (3x-y)^2+(3x+y)(3x-y),x=1,y=-2 {(x+2)^2-(y-3)^2=(x+y)(x-y) {x-3y=2 2（x+y)-3(x-y)=3 ,4(x+y)+3(x-y)=15 计算：y(x-y)^2+(y-x)^3=?