9514 1404 393
Answer:
[tex]\displaystyle S_n=\sum_{k=1}^n{4(-3)^{k-1}}[/tex]
Step-by-step explanation:
The first term of this geometric series is 4. The common ratio is -12/4 = -3, so the general term is ...
an = 4·(-3)^(n-1)
The sum is the sum of terms of this form.
[tex]\displaystyle S_n=\sum_{k=1}^n{4(-3)^{k-1}}[/tex]
