/x/=2007,/y/=2008,x＞0,y＜0,求x+y的值

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 化简 x / y(x+y) - y / x(x+y) = 已知x=2007,y=2008,则(x+y)*(x^2+y^2)/(x^4-y^4)=__ /x-y/=x-y,且/x/=2007,/y/=2008,求x+y的值 y=x(x /x/=2007,/y/=2008,x＞0,y＜0,求x+y的值 x(x+y)(x-y)-y(y+x)(y-x)=(x-y)( )填空 |x|=99 |y|=98 x＞y x, x^2+y^2=15,x+y=7,x＞y,求x-y Y=|x+2009|+|x+2008|+|x-1|+|x-2|+……+|x-2007|+|x-2008|+|x-2009|,x取何值时Y最小? 已知x,y且x>y,如果2007x^2+x=2008y^2+y,那么x-y是否为完全平方数 x+x+x+x+y+y+y=56 1.x=2007,y=2008,求分式（x+y)(x²+y²）/x四次方-y四次方2.已知x/y=3,求x²+y²-xy/x²-y²的值 已知实数x,y满足(x-根号x^2-2008)(y-根号y^2-2008)=2008 ,则3x^2-2y^2+3x-3y-2007已知实数x,y满足【x-根号下（x^2-2008）】【y-根号下（y^2-2008)】=2008 ,则3x^2-2y^2+3x-3y-2007的值是 推倒公式:(x+y)(x*x-3x+y*y)=x*x*x+y*y*y怎么做. x+x+x+y+y=6.4 y+y+y+x+x=7.1 怎么算? x+x+y+y+y=21 ,x+x+y+y+y+y+y=27 ,x ,y=? x+x+y+y+y=21 ,x+x+y+y+y+y+y=27 ,x ,y=?