The values of a1, n, and r are given for the following geometric sequences. Find the sum of the terms of each sequence:

The sum of the tems of the series are given by

S_n  =  a₁ [ 1  + r^n ] / [1 - r ] 

So....the sum of the first 4 terms  =

-2 [ 1 - (-3)^4] / [ 1  - (-3) ] =

-2 [ -80] / [4]  =

160 / 4   = 

40

The values of a1, n, and r are given for the following geometric sequences. Find the sum of the terms of each sequence:

 a1 = –2, n = 4, r=–3  

Sum=40