Find the sum.
-(-6)+ (-1)+ 4 + 9 + ... + 39
A)165
B)170
C)160
D)330

Question

Quizplus · Accepted Answer

The given sequence is an arithmetic sequence with the first term $a_1 = -6$, common difference $d = 5$, and the last term $a_n = 39$. To find the sum, we first need to determine the number of terms $n$. We can use the formula for the $n$th term of an arithmetic sequence: $a_n = a_1 + (n - 1)d$. Substituting the given values, we get $39 = -6 + (n - 1)5$. Solving for $n$ gives us $n = 10$. Now, we can use the formula for the sum of an arithmetic series: $S_n = \frac{n}{2}(a_1 + a_n)$. Substituting the known values, we get $S_{10} = \frac{10}{2}(-6 + 39) = 5 \times 33 = 165$.

Find the Sum. -(-6)+ (-1)+ 4 + 9 + ... + 39