Question
Multiple Choice $\sum_{k=1}^{n} k=1+2+3+\cdots+n=$ ________.(a) $n !$(b) $\frac{n(n+1)}{2}$(c) $n k$(d) $\frac{n(n+1)(2 n+1)}{6}$
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Step 1: We are given a series $\sum_{k=1}^{n} k=1+2+3+\cdots+n$. Show more…
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$\sum_{k=1}^{n} k=1+2+3+\cdots+n=$_____. $$ \begin{array}{ll}{\text { (a) } n !} & {\text { (b) } \frac{n(n+1)}{2}} \\ {\text { (c) } n k} & {\text { (d) } \frac{n(n+1)(2 n+1)}{6}}\end{array} $$
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