Answer
$28$
Work Step by Step
$\sum ^{5}_{i=-1}\left( i^{2}-2i\right) =\left( \left( -1\right) ^{2}-2\left( -1\right) \right) +\left( 0^{2}-2\times 0\right) +\left( 1^{2}-2\times 1\right) +\left( 2^{2}-2\times 2\right) +\left( 3^{2}-2\times 3\right) +\left( 4^{2}-2\times 4\right) +\left( 5^{2}-2\times 5\right) =28$
