Answer
$2049$
Work Step by Step
The general formula to find the nth partial sum of a Geometric sequence is given as: $ S_{n}=\dfrac{a(1-r^n)}{(1-r)}$
$ r=\dfrac{a_2}{a_1}=\dfrac{-6}{3}=-2$ and $ n=11$
Now, $ S_{11}=\dfrac{3(1-(-2)^{11})}{(1-(-2))}=3 \times \dfrac{2049}{3}$
Our answer is: $ S_{11}=2049$
