(2x-1)/5+(3y-2)/4=2 (3x+1)/3-(3y+2)/4=3/4

化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-( （x+2)(x+3) (x-4)(x+1) (y+4)(y-2) (y-5)(y-3) 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 3x-2y=1 4x-5y [(2x+y)^2+(y+2x)(y-2x)-2y(4x-y)]/4y,其中x=1/2,y=1/3 先化简,再求值：[(x+y)(x-y)-(x-y)^2+2y(x-3y)]/(-4y),其中x=1,y=-2 9y=3x-(x-1),4(x+y)-(2x+4)=8y 化简求值{(x=2y)(5x-2y)-(3x+2y)(3x-2y)]/4x,其中x=2,y=-1 若x=-1/4,能否确定代数式(2x-y)(2x+y)+(2x-y)(y-4x)+2y(y-3x)的值? 3x+2y/4=2x+y/5=x-y+1/6