Question 472812
The common ratio is -2/1 = -2
The sum of the first n terms of a geometric sequence is:
{{{a(1-r^n)/(1-r)}}} where a is the 1st term of the sequence
Putting in n = 6, a = 1 and r = -2, we get:
Sum = {{{(1-(-2)^6)(1- -2)}}} -> {{{(1-64)/(1 - -2)}}}
This gives Sum = -21