数列An的前n项和为Sn,若an=1⼀n(n+1),则S6等于?

2025-02-24 05:55:32
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回答1:

an=1/n-1/(n+i)则 s6=a1+a2+a3+a4+a5+a6=1-1/2+1/2-1/3....+1/6-1/7=1-1/7=6/7