已知Sn=1/1+根号2+1/根号2+根号3+1/根号3+2.+1/根号n+根号n+1求SN 急用
问题描述:
已知Sn=1/1+根号2+1/根号2+根号3+1/根号3+2.+1/根号n+根号n+1求SN 急用
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答
看通项:1/(√n+√n+1)=√n+1-√n,所以求和=√n+1-1
已知Sn=1/1+根号2+1/根号2+根号3+1/根号3+2.+1/根号n+根号n+1求SN 急用
....
看通项:1/(√n+√n+1)=√n+1-√n,所以求和=√n+1-1