Find the sum of the series.
-$$\sum _ { n = 1 } ^ { \infty } \frac { 7 } { 3 ^ { n } }$$
A) $\frac { 21 } { 2 }$
B) $\frac { 21 } { 4 }$
C) $\frac { 7 } { 2 }$
D) $\frac { 7 } { 4 }$

Question

Quizplus · Accepted Answer

We can use the formula for sum of an infinite geometric series with first term $a=7$ and common ratio $r=\frac{1}{3}$
$$\frac{a}{1-r}=\frac{7}{1-\frac{1}{3}}=\frac{7}{\frac{2}{3}}=\frac{21}{2}$$
Therefore, the answer is choice letter $\boxed{\textbf{(A)}}$.

Find the Sum of the Series ∑n=1∞73n\sum _ { n = 1 } ^ { \infty } \frac { 7 } { 3 ^ { n } }n=1∑∞​3n7​

Find the Sum of the Series $\sum _ { n = 1 } ^ { \infty } \frac { 7 } { 3 ^ { n } }$