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裂项相消法隔项相消原式=1/2[(1-1/3)+(1/2-1/4)+(1/3-1/5)+.+(1/n-1/(n+2))]请问怎样求和?请写出具体计算过程.1/2(3/2-1/(n+1)-1/(n+2))请问为什么是1/(n+1)?
题目详情
裂项相消法 隔项相消
原式=1/2[(1-1/3)+(1/2-1/4)+(1/3-1/5)+.+(1/n-1/(n+2))]
请问怎样求和?请写出具体计算过程 .
1/2(3/2-1/(n+1)-1/(n+2)) 请问为什么是1/(n+1)?
原式=1/2[(1-1/3)+(1/2-1/4)+(1/3-1/5)+.+(1/n-1/(n+2))]
请问怎样求和?请写出具体计算过程 .
1/2(3/2-1/(n+1)-1/(n+2)) 请问为什么是1/(n+1)?
▼优质解答
答案和解析
1/2[(1-1/3)+(1/2-1/4)+(1/3-1/5)+.+(1/n-1/(n+2))]
=1/2(1-1/3+1/2-1/4+1/3-1/5+.+1/n-1/n+2)
=1/2(1+1/2-1/(n+1)-1/(n+2))
=1/2(3/2-1/(n+1)-1/(n+2))
=1/2(1-1/3+1/2-1/4+1/3-1/5+.+1/n-1/n+2)
=1/2(1+1/2-1/(n+1)-1/(n+2))
=1/2(3/2-1/(n+1)-1/(n+2))
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