Use summation notation to write the sum. $- 3 - 6 - 12 - \ldots - 48$
A) $\sum _ { n = 1 } ^ { 5 } - 3 ( 2 ) ^ { n - 1 }$
B) $\sum _ { n = 1 } ^ { 4 } - 3 ( 2 ) ^ { n + 1 }$
C) $\sum _ { n = 0 } ^ { 4 } - 3 ( 2 ) ^ { n - 1 }$
D) $\sum _ { n = 1 } ^ { 3 } - 3 ( 2 ) ^ { n }$
E) $\sum _ { n = 1 } ^ { 3 } - 3 ( 2 ) ^ { n - 1 }$

Question

Quizplus · Accepted Answer

The sequence is a geometric sequence with the first term $a = -3$ and common ratio $r = 2$. The formula for the $n$th term of a geometric sequence is $a \cdot r^{n-1}$. The sequence goes up to $-48$, which is the fifth term, so the summation should run from 1 to 5, matching option A.

Use Summation Notation to Write the Sum −3−6−12−…−48- 3 - 6 - 12 - \ldots - 48−3−6−12−…−48

Use Summation Notation to Write the Sum $- 3 - 6 - 12 - \ldots - 48$