(1)已知x^2+y^2=5,xy=2,求1/(1/x+1/y)的值.(2)计算:1/(a-x)-1/(a+x)-2x/(a^2+x^2)-(4x^3)/(a^4+x^4)+……(1)已知x^2+y^2=5,xy=2,求1/(1/x+1/y)的值.(2)计算:1/(a-x)-1/(a+x)-2x/(a^2+x^2)-(4x^3)/(a^4+x^4)+(8x^7)/(x^8-a^8).麻烦写得详细一点.

已知xy/x+y=1/2,则代数式3x-5xy+3y/-x+3xy-y= 已知x+y=-1,xy=-2,求代数式-5（x+y)+(x-y)+x(xy+y)的值 已知x+y=1,xy=-2,则x²y+xy²-2xy 已知x+y=1,xy=1/5,则x^2y=xy^2 已知x+y=-1,xy=-2,求代数式-5（x+y)+(x-y)+2(xy+y)的值 已知xy^2=-2,求-xy（x^2y^5-xy^3-y)的值. 已知xy^2=-2 求-xy(x^2y^5-xy^3-y) 已知xy^2=-2xy(x^2y^5-xy^3-y) 【数学】已知 1/x-1/y=3 求 5x-xy-5y / x-2xy-y=?已知 1/x=1/y 求 2x-3xy-2y / x-2xy-y=? 已知1/x+1/y=5,求x+y+3xy/2x-4xy+2y的值,已知1/x+1/y=5,x+y+3xy/2x-4xy+2y的值, 已知x^2-xy=5,xy-y^2=-3求3(x^2-xy)-xy+y^2 已知 1/x-1/y=2,求2x+5xy-2y/x-2xy-y 已知1/x+1/y=5,则2x-5xy+2y/x+2xy+y 已知(1/x)-(1/y)=5,求(2x+5xy-2y)/(x-2xy-y) 已知1/x+1/y=5,则2x-5xy+2y/x+2xy+y详解 已知1/x=3+1/y,则(2x-5xy-2y)/(y+3xy-x)=_______. 已知1/x+1/y=5 求2x-3xy+2y/3x+2xy+3y 已知1/x+1/y=5 求2x-3xy+2y/x+2xy+y