Answer
$-105$
Work Step by Step
See p. 861.
For the geometric sequence $a_{n}=ar^{n-1}$
the nth partial sum$ S_{n}=\displaystyle \sum_{k=1}^{n}ar^{k-1}$ (where $r\neq 1$)
is given by$ \displaystyle \quad S_{n}=a\cdot\frac{1-r^{n}}{1-r}$
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$S_{n}=5\displaystyle \cdot\frac{1-(-2)^{6}}{1-(-2)}=5\times\frac{-63}{3}$
$=-5\times 21$
$=-105$