(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.
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![(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.](/uploads/image/z/3007612-28-2.jpg?t=%281%29%E5%B7%B2%E7%9F%A5x%5E2%2By%5E2%3D5%2Cxy%3D2%2C%E6%B1%821%2F%281%2Fx%2B1%2Fy%29%E7%9A%84%E5%80%BC.%282%29%E8%AE%A1%E7%AE%97%3A1%2F%28a-x%29-1%2F%28a%2Bx%29-2x%2F%28a%5E2%2Bx%5E2%29-%284x%5E3%29%2F%28a%5E4%2Bx%5E4%29%2B%E2%80%A6%E2%80%A6%281%29%E5%B7%B2%E7%9F%A5x%5E2%2By%5E2%3D5%2Cxy%3D2%2C%E6%B1%821%2F%281%2Fx%2B1%2Fy%29%E7%9A%84%E5%80%BC.%282%29%E8%AE%A1%E7%AE%97%3A1%2F%28a-x%29-1%2F%28a%2Bx%29-2x%2F%28a%5E2%2Bx%5E2%29-%284x%5E3%29%2F%28a%5E4%2Bx%5E4%29%2B%288x%5E7%29%2F%28x%5E8-a%5E8%29.%E9%BA%BB%E7%83%A6%E5%86%99%E5%BE%97%E8%AF%A6%E7%BB%86%E4%B8%80%E7%82%B9.)
(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.
(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.^2是平方的意思.^3是立方的意思.^4是四次方.^7是七次方.^8是八次方.
(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.
(1)已知x^2+y^2=5 [1]
xy=2 [2]
[1]+[2]*2 (x+y)^2=9
x+y=±3
所以1/(1/x+1/y)=xy/(x+y)=2/(±3)=±2/3
(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).
=(a+x-a+x)/(a^2-x^2)-2x/(a^2+x^2)-(4x^3)/(a^4+x^4)+(8x^7)/(x^8-a^8).
=2x*(a^2+x^2-a^2+x^2)/(a^4-x^4)-(4x^3)/(a^4+x^4)+(8x^7)/(x^8-a^8).
=4x^3*(a^4+x^4-a^4+x^4)/(a^8-x^8)+(8x^7)/(x^8-a^8).
=8x^7/(a^8-x^8)-8x^7/(a^8-x^8)
=0
(1)x+y=±3,1/(1/x+1/y)=xy/(x+y)=±1/3
(2)先将前两项通分,再与第3项通分,再依次与第4项,第5项通分即可得出结果。