Use the partial sum formula to find the partial sum of the given geometric sequence.
-Find the sum of the first five terms of the geometric sequence $1,2,4 , \ldots$
A) $\frac { 31 } { 5 }$
B) $\frac { 91 } { 15 }$
C) $\frac { 91 } { 3 }$
D) 31

Question

Quizplus · Accepted Answer

The partial sum of a geometric sequence can be found using the formula $S_n = \frac{a(1 - r^n)}{1 - r}$, where $S_n$ is the sum of the first $n$ terms, $a$ is the first term, $r$ is the common ratio, and $n$ is the number of terms. Here, $a = 1$, $r = 2$, and $n = 5$. Plugging these values into the formula gives $S_5 = \frac{1(1 - 2^5)}{1 - 2} = \frac{1 - 32}{-1} = 31$.

Use the Partial Sum Formula to Find the Partial Sum 1,2,4,…1,2,4 , \ldots1,2,4,…

Use the Partial Sum Formula to Find the Partial Sum $1,2,4 , \ldots$