How do you find the sum of Sigma (3i-1) from i=1 to 6?

Sep 22, 2017

57

Explanation:

${\Sigma}_{1}^{6} \left(3 i - 1\right)$
-1 is repeated 6 times
${\Sigma}_{1}^{6} \left(3 i\right) - 6$
$= 3 \left(1 + 2 + 3 + 4 + 5 + 6\right) - 6$
$= 3 \left(21\right) - 6$
$= 63 - 6 = 57$