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学习数列时,我们需要不断的归纳总结.请看下面的例子. ①已知an=n(n+1)求Sn. ②已知an=n(n+1)(n+2)求Sn. 常用解法①解∵an=n(n+1)=n2+n, ∴Sn=12+22+32+…+
When learning the sequence, we need to continue to summarize. See the following example. 1 Known an=n(n+1) Find Sn. 2 Known an=n(n+1)(n+2) Find Sn. Common solution 1 solution =an=n(n+1)=n2+n, ∴Sn=12+22+32+...+