已知x=2013,y=2014,则(x+y)(x^2+y^2)/x^4-y^4=?

已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 已知4x=9y求(1)x+y/y (2)y-x/2x 已知2x-y=10,求[(x²+y²)-(x-y)²+2y(x-y)]/4y 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? 已知x/y=2,求2x(x+y)-y(x+y)/4x²-4xy+y² 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-( 已知x²+y²+5=2x+4y,求【2x²-(x-y)(x-y)】【(x+y-1)(x-y 已知x-2y/2x+3y=3/4,则x：y= 已知x²+4x+y²-2y+5=0,则x+y= 已知y/x=2,则求代数式x+y/4x-5y的值 已知正实数x，y满足x+2y=4，则1x+1y 已知X-Y/X+Y=3,求代数式2(x-y)/X+Y-3X+Y/X+Y