1/4x^2y-3x^2+3/4x^2y+2x^2合并同类项

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) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= (x+3y-4)(2x-y) 计算（2x-3y)(x+4y)-(3x+y)(x-2y)（2x-3y)(x+4y)-(3x+y)(x-2y) 1/(x-y)+1/(x+y)+2x/(x^2+y^2)+4x^3/(x^4+y^4)化简 因式分解(x-2y)(x-3y)+(x-4y)(x-5y)+（x-3y)(x-5y)+(x-2y)(x-4y) x+y+2(-x-y+1)=3(1-y-x)-4-(y+x-1),x+y=? 先化简 再求值 (2x-y)(y+x)-(x-2y)(2y+x)-(-3y+x)^2其(√x+1)+y^2+4=-4y 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-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 (2x+y)(2x-3y)+x(2y+y) 2a(x-y)-4b(x-y) (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 9y=3x-(x-1),4(x+y)-(2x+4)=8y 4x(x-y)-(2x-3y)(2x-3y) x=1 y=-1 [(y-2x)(-2x-y)+4(x-2y)平方]/3y,其中x=1,y=-3