Use the formula for S n to find the sum of the first five terms of the geometric sequence.
-$3,9,27,81 , \ldots$
A) 360
B) 353
C) 363
D) 365

Question

Quizplus · Accepted Answer

The given sequence is a geometric sequence with the first term $a = 3$ and common ratio $r = 3$. The sum of the first $n$ terms of a geometric sequence is given by $S_n = \frac{a(1 - r^n)}{1 - r}$ for $r \neq 1$. Substituting $a = 3$, $r = 3$, and $n = 5$, we get $S_5 = \frac{3(1 - 3^5)}{1 - 3} = \frac{3(1 - 243)}{-2} = \frac{3(-242)}{-2} = 363$.

Use the Formula for Sn to Find the Sum of the First

Use the Formula for S_n to Find the Sum of the First