Find the sum,m, $\mathrm { s } _ { \mathbf { n } },$ , o f the sequence.
--13, -23, -33, -43, . . ., -703
A)-25,410
B)-713
C)-25,060
D)-25,051

Question

Quizplus · Accepted Answer

The sequence is an arithmetic sequence with the first term $a = -13$ and common difference $d = -10$. The last term is $-703$. To find the number of terms $n$, use the formula for the nth term of an arithmetic sequence: $a_n = a + (n-1)d$. Solving $-703 = -13 + (n-1)(-10)$ gives $n = 70$. The sum of an arithmetic sequence is given by $S_n = \frac{n}{2} (a + a_n)$. Substituting the values, $S_{70} = \frac{70}{2}(-13 - 703) = -25,060$.

Find the Sum,m sn,\mathrm { s } _ { \mathbf { n } },sn​,

Find the Sum,m $\mathrm { s } _ { \mathbf { n } },$