Find the sum of the first 4 terms of the arithmetic sequence with first term -13 and common difference -2 .
A) -64
B) -21
C) -52
D) -13

Question

Find the sum of the first 4 terms of the arithmetic sequence with first term  -13  and common difference  -2 .
A)  -64 
B)  -21 
C)  -52 
D)  -13

Quizplus · Accepted Answer

The sum of the first 4 terms of an arithmetic sequence can be found using the formula $S_n = \frac{n}{2} [2a + (n-1)d]$, where $S_n$ is the sum of the first $n$ terms, $a$ is the first term, $d$ is the common difference, and $n$ is the number of terms. Plugging in the values given ($a = -13$, $d = -2$, $n = 4$), we get $S_4 = \frac{4}{2} [2(-13) + (4-1)(-2)] = 2[-26 - 6] = 2[-32] = -64$.

Find the Sum of the First 4 Terms of the Arithmetic