x/2+y/3=2,2x+3y=19 解方程.

(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)=? x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 【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 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 解二元一次方程组：3(x+y)-4(x-y)=4,x+y/2+x-y/6+1x+y/2+x-y/6+1=1 x-y/x+y=-1/2,x*x-xy-2y*y/x*x-3xy+2y*y的解是多少?同上,请将过程写出, {(x+2)^2-(y-3)^2=(x+y)(x-y) {x-3y=2 (3x-y)^2+(3x+y)(3x-y),x=1,y=-2 x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2 (-x+2y)(2x+y)-(2x+y)(y-2x)-3xy=?因式分解 2（x+y)-3(x-y)=3 ,4(x+y)+3(x-y)=15 计算：y(x-y)^2+(y-x)^3=? y'=(2x+y)/(3x-y)微分方程通解