Question

Calculate the following sum.
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Answer 1

$\displaystyle\\(k+1)(k-1)=k^2-1\\\sum\limits_{k=1}^{10}(k^2-1)=\sum\limits_{k=1}^{10}k^2-1\cdot10=\frac{10\cdot(10+1)\cdot(2\cdot10+1)}{6}-10=\frac{10\cdot11\cdot21}{6}-\\-10=385-10=375$

Ответ: 375