# How do you use summation notation to write the arithmetic series -3.9+(-1.9)+.1+... for six terms?

${\sum}_{n = 0}^{5} \left(- 3.9 + 2 n\right) = 6.6$
${\sum}_{n = 0}^{5} \left(- 3.9 + 2 n\right) = - 3.9 \cdot 6 + 2 {\sum}_{n = 0}^{5} n =$
$= - 23.4 + 2 \cdot \frac{5 \left(5 + 1\right)}{2} = - 23.4 + 30 = 6.6$