(1/2x^4y^2-1/3x^3y^3-3/4x^2y^4)÷(-2/3X^2Y^2)

x²/xy-x/y 3x/4x+y - x-2y/4x+y (1-y/y+x)÷x/y²-x² {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 x+y+2(-x-y+1)=3(1-y-x)-4-(y+x-1),x+y=? 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) 先化简 再求值 (2x-y)(y+x)-(x-2y)(2y+x)-(-3y+x)^2其(√x+1)+y^2+4=-4y 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-y=1,求[(x+2y)^2+(2x+y)(x-4y)-3(x+y)(x-y)]除以y的值大神们帮帮忙 已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值 1/(x-y)+1/(x+y)+2x/(x^2+y^2)+4x^3/(x^4+y^4)化简 (x/x+y +2y/x+y)乘以xy/ x+2y除以(1/x+1/y)（2）（3x^2/4y)^2乘以2y/3x+ x^2/2y^2除以2y^2/x [(y-2x)(-2x-y)+4(x-2y)平方]/3y,其中x=1,y=-3 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x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 9y=3x-(x-1),4(x+y)-(2x+4)=8y 为什么(x-2y)(x+4y)-(x-2y)+3(x+4y)-3=(x-2y+3)(x+4y-1). 4x(x-y)-(2x-3y)(2x-3y) x=1 y=-1 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