Find the sum of the first n terms of the following arithmetic sequence.
-$a _ { 1 } = - 7 , d = 2 ; n = 5$
A) -35
B) -15
C) 3
D) -10

Question

Quizplus · Accepted Answer

The sum of the first n terms of an arithmetic sequence can be found using the formula $S_n = \frac{n}{2} [2a_1 + (n-1)d]$, where $S_n$ is the sum of the first n terms, $a_1$ is the first term, $d$ is the common difference, and $n$ is the number of terms. Plugging in the given values: $S_5 = \frac{5}{2} [2(-7) + (5-1)2] = \frac{5}{2} [-14 + 8] = \frac{5}{2} (-6) = -15$.

Find the Sum of the First N Terms of the Following