Use the formula for the sum of the first n terms of an arithmetic sequence to find the indicated sum.
-$$\sum _ { i = 1 } ^ { 36 } ( 2 i + 3 )$$
A) 1440
B) 1404
C) 1620
D) 1746

Question

Quizplus · Accepted Answer

The formula for the sum of the first n terms of an arithmetic sequence is:$$S_n = \frac{n}{2}(a_1 + a_n)$$where $a_1$ is the first term, $a_n$ is the nth term, and n is the number of terms.In this case, $a_1 = 5$, $a_n = 2(36) + 3 = 75$, and $n = 36$. So, the sum of the first 36 terms is:$$S_{36} = \frac{36}{2}(5 + 75) = 18(80) = 1440$$

Use the Formula for the Sum of the First N ∑i=136(2i+3)\sum _ { i = 1 } ^ { 36 } ( 2 i + 3 )i=1∑36​(2i+3)

Use the Formula for the Sum of the First N $\sum _ { i = 1 } ^ { 36 } ( 2 i + 3 )$