2【x+y】-3【x-y】=7 3【x+y】+5【x-y】=1 有几种方法,哪种方法简便,试试看

若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 化简3(x-y)-7(x--y)+2(y-x) (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) 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) (x+y)(2x-3y)=? x(x-y)2-(y-x)3 3x+5y-(x+y)=6 2(x+y)-3x=-7 7y(x-3y)-2(3y-x)=0 .x=?,y=? [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 化简3x-2/(x+y)[(x+y)/3x-x-y]÷(x-y)/x 3^x+2x=y,x 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 【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