用数学归纳法证明:(n+1)(n+2)(n+3)+.......+(n+n)=(2^n)*1*3*.....(2n-1)
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n=1时,2=2成立
假设n=k时,(k+1)(k+2)(k+3).......(k+k)=(2^k)*1*3*.....(2k-1)成立
则当n=k+1时,
(k+2)(k+3).......(k+1+k-1)(k+1+k)(k+1+k+1)
=(k+2)(k+3).......(k+k)(k+1+k)2(k+1)
=(2^k)*1*3*.....(2k-1)*2*(2k+1)
=(2^k+1)*1*3*.....(2k-1)(2k+1)
所以:(n+1)(n+2)(n+3).......(n+n)=(2^n)*1*3*.....(2n-1)
好辛苦 给分吧
假设n=k时,(k+1)(k+2)(k+3).......(k+k)=(2^k)*1*3*.....(2k-1)成立
则当n=k+1时,
(k+2)(k+3).......(k+1+k-1)(k+1+k)(k+1+k+1)
=(k+2)(k+3).......(k+k)(k+1+k)2(k+1)
=(2^k)*1*3*.....(2k-1)*2*(2k+1)
=(2^k+1)*1*3*.....(2k-1)(2k+1)
所以:(n+1)(n+2)(n+3).......(n+n)=(2^n)*1*3*.....(2n-1)
好辛苦 给分吧
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