Find the indicated partial sum for the given sequence with the given first term and general term
-$\mathrm{s}_{5}, \mathrm{a}_{1}=-1, \mathrm{a}_{\mathrm{n}}=-10 \mathrm{a}_{\mathrm{n}}-1$
A) - 950
B) 1049
C) 1050
D) - 9091

Question

Quizplus · Accepted Answer

The sequence is geometric with the first term $a_1 = -1$ and the common ratio $r = -10$. The formula for the sum of the first $n$ terms of a geometric sequence is $S_n = a_1 \frac{r^n - 1}{r - 1}$. For $n = 5$, $S_5 = -1 \frac{(-10)^5 - 1}{-10 - 1} = -1 \frac{-100000 - 1}{-11} = -9091$.

Find the Indicated Partial Sum for the Given Sequence with the Given