恒等式,求证

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恒等式,求证
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恒等式,求证
恒等式,求证

恒等式,求证
证明:
可以利用数学归纳法
(1)当n=1时,左=1-1/2=1/2=右成立
(2)假设n=k(k≥1)时等式成立,即:
1-1-1/2+1/3-1/4+……+1/(2k-1)-1/2k=1/(k+1)+1/(k+2)+……1/(2k)
则当n=k+1时
左=[1-1/2+1/3-1/4+……+1/(2k-1)-1/(2k)]+1/(2k+1)-1/(2k+2)
=[1/(k+1)+1/(k+2)+……1/(2k)]+1/(2k+1)-1/(2k+2)
=1/(k+2)+……1/(2k)+[1/(k+1)+1/(2k+1)-1/(2k+2)]
=1/(k+2)+……1/2k+[1/(2k+1)+1/(2k+2)]=右
所以当n=k+1时等式也成立
综上,由(1)(2)等式对任意的n都成立,
得证