Question 1154282
Find the sum of the geometric sequence −3, 15, −75, 375, … when there are 7 terms and select the correct answer below.

the options are:
A) -39,063
B) 39,063
C) 58,593
D) -58,593

if you can, please include a thorough explanation!!! thanks!
<pre>Use the formula for the sum of a GP: {{{matrix(1,3, S[n], "=", a[1](1 - r^n)/(1 - r))}}}
{{{matrix(1,3, S[7], "=", (- 3(1 - (- 5)^7))/(1 - - 5))}}} ---- Substituting {{{matrix(3,3, 7, for, n, - 3, for, a[1], - 5, for, r)}}} 
{{{matrix(1,3, S[7], "=", (- 3(1 - (- "78,125")))/(1 + 5))}}} 
{{{matrix(1,3, S[7], "=", (- 3(1 + "78,125"))/6)}}} 
{{{matrix(1,3, S[7], "=", (- 3("78,126"))/6)}}} 
Sum of the 7 GP terms, or: {{{highlight_green(matrix(1,5, S[7], "=", - 3("13,021"), "=", highlight(- "39,063")))}}}