1/(x-y)+1/(x+y)+2x/(x^2+y^2)+4x^3/(x^4+y^4)

（x+2)(x+3) (x-4)(x+1) (y+4)(y-2) (y-5)(y-3) {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 1、x(x-y)(x+y)-x(x+y)^2 1) (2x+5y)(2x-5y)(-4x^2-25y^2) 2) [（x+y)(x-y)-(x-y)^2+2y(x-y x/x-y*y^2/x+y-x^3y2/x^4-y^4/x^2/x^2+y^2 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-( 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 (x+3y-4)(2x-y) 已知4x=9y求(1)x+y/y (2)y-x/2x x^2-y^2/x+y-4x(x-y)+y^2/2x-y, 9y=3x-(x-1),4(x+y)-(2x+4)=8y