Question

Evaluate the summation of 3 times negative 2 to the n minus 1 power, from n equals 1 to 5..

Answer 1

I assume this is the question?
\[\sum_{n=1}^{5} 3(-2)^{n-1}\]

Answer 2

You could either plug in n=1,2,3..5 and add all the final values or use the formula for the sum of a finite geometric series.

\[S_{n}=a_{1}(\frac{ 1-r^n }{ 1-r })\]
wherein
n=# of terms
a1=first term
r=common ratio