(-1/4x^2+12x^3y^2-8x^4y)/(-1/2x^2y)=?

{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 9y=3x-(x-1),4(x+y)-(2x+4)=8y 计算:1/(x-y)-1/(x+y)-2y/(x^2+y^2)-4y^3/(x^4+y^4)-8x^7/(x^8+y^8 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-( 1、x(x-y)(x+y)-x(x+y)^2 （x+2)(x+3) (x-4)(x+1) (y+4)(y-2) (y-5)(y-3) 已知4x=9y求(1)x+y/y (2)y-x/2x 若x=-1/4,能否确定代数式(2x-y)(2x+y)+(2x-y)(y-4x)+2y(y-3x)的值? [(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 1) (2x+5y)(2x-5y)(-4x^2-25y^2) 2) [（x+y)(x-y)-(x-y)^2+2y(x-y