Answer
104975
Work Step by Step
$\sum_{i=1}^{n}(i^3-2i)=\sum_{i=1}^ni^3-2\sum_{i=1}^ni$
$=\frac{n^2(n+1)^2}{4}-2\times\frac{n(n+1)}{2}=\frac{n^2(n+1)^2}{4}-n(n+1)$
Therefore,
$\sum_{i=1}^{25}(i^3-2i)=\frac{25^2(26)^2}{4}-25(26)=104975$
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