用归纳法证明 1/2×4+1/4×6+1/6×8+…+1/2n(2n+2)=n/4(n+1)

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用归纳法证明 1/2×4+1/4×6+1/6×8+…+1/2n(2n+2)=n/4(n+1)
用归纳法证明 1/2×4+1/4×6+1/6×8+…+1/2n(2n+2)=n/4(n+1)

用归纳法证明 1/2×4+1/4×6+1/6×8+…+1/2n(2n+2)=n/4(n+1)
证:
n=1时,
右边=1/[4×(1+1)]=1/(2×4)=左边,等式成立.
假设当n=k(k∈N+且k≥1)时,等式成立,即
1/(2×4)+1/(4×6)+...+1/[2k(2k+2)]=k/[4(k+1)]
则当n=k+1时,
1/(2×(4)+1/(4×(6)+...+1/[2k(2k+2)]+1/[(2k+2)(2k+4)]
=k/[4(k+1)]+1/[4(k+1)(k+2)]
=[k(k+2)+1]/[4(k+1)(k+1+1)]
=(k²+2k+1)/[4(k+1)(k+1+1)]
=(k+1)²/[4(k+1)(k+1+1)]
=(k+1)/[4(k+1+1)]
等式同样成立.
综上,得1/(2×4)+1/(4×6)+...+1/[2n(2n+2)]=n/[4(n+1)]