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问题: 数学题(图片)

要全过程,谢谢!

解答:

S+1/(1-x)=1/(1-x)+1/(1+x)+2/(1+x^2)+2^2/(1+x^4)+....2^n/(1+x^(2^n))
S+1/(1-x)=[1/(1-x)+1/(1+x)]+2/(1+x^2)+2^2/(1+x4)+....2^n/(1+x^(2^n))
S+1/(1-x)=2/(1-x^2)+2/(1+x^2)+2^2/(1+x^4)+....2^n/(1+x^(2^n))
S+1/(1-x)=2^2/(1-x^4)+2^2/(1+x^4)+....2^n/(1+x^(2^n)
................................................
S+1/(1-x)=2^n/(1-x^2^n))+2^n/(1+x^(2^n))
S+1/(1-x)=2^(n+1)/[1-x^2^(n+1))]
∴S=2^(n+1)/[1-x^2^(n+1))]-1/(1-x)