Question 550239
First we need to know the formula of a geometric series:

Its

{{{s=a((1-r^n)/(1-r))}}}
Where s=sum, a=the first term r is the ratio and n is the number of terms

We know most of the info already
{{{-189=a((1-2^6)/(1-2))}}}
-189=a(1-64)/-1
{{{-189=a*-63*-1}}}
{{{-189=a*63}}}
a=-3

You won't have to do this step, but to get a feel for the series, here's our terms -3,-6,-12,-24,-48,-96 and they do equal -189