## Intermediate Algebra (6th Edition)

$S_{5} =-25$
Sum of the first five negative odd integers. Sequence $-1,-3,-5,-7,-9$ is an arithmetic sequence $a_{1} = -1$ $a_{n} = -9$ To find sum of first five terms, substitute $a_{1},a_{n}$ and $n=5$ in $S_{n} = \frac{n}{2} (a_{1}+a_{n})$ $S_{5} = \frac{5}{2} (-1-9)$ $S_{5} = \frac{5}{2} (-10)$ $S_{5} =-25$