{3x+7y=3 2x+9y=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 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= (x+y)(x-y)+(x-y)平方-(x-y)(3x-y) 其中x=-2 y=3分之一 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) (x+y)(2x-3y)=? 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) x-2y=9 x+y+z=7 2x-3y=12 7y(x-3y)-2(3y-x)=0 .x=?,y=? 【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 数学题求解解下列方程组x+y/2 +x-y/3=62(x+y)-x=-49x+7y=397x+9x=41 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 3x+5y-(x+y)=6 2(x+y)-3x=-7 9y=3x-(x-1),4(x+y)-(2x+4)=8y