## Intermediate Algebra for College Students (7th Edition)

$-258$
Since, we have $S_n=\dfrac{a_1(1-r^{n})}{1-r}$ Here, $n=7,a_1=-6,r=-2$ Thus, $S_{7}=\dfrac{-6[1-(-2)^{7}]}{1-(-2)}=\dfrac{-6}{3}(129)=-258$