Answer
$-621,937,812$
Work Step by Step
$\dfrac{a_{n+1}}{a_n}=\dfrac{2(-6)^{n+1}}{2(-6)^n}=-6$
Since the ratio between consecutive terms is constant, the given sequence is geometric.
The formula for the sum of the first $n$ terms is:
The first term is $a_{1}=2(-6)^{1}=-12$.
The common ratio is $r=-6$.
$S_{n}=\frac{a_{1}(1-r^{n})}{1-r}$
$S_{11}=\frac{-12(1-(-6)^{11})}{1-(-6)}=-621,937,812$
