Use the Formula for the Sum of the First n Terms of an Arithmetic Sequence
-Find the sum of the first 30 terms of the arithmetic sequence: 7, 3, -1, -5, . . .
A) -1530
B) -1520
C) -113
D) -1590

Question

Quizplus · Accepted Answer

The sum of the first n terms of an arithmetic sequence is given by the formula S_n = n/2 * (2a + (n-1)d), where a is the first term, d is the common difference, and n is the number of terms. Here, a = 7, d = 3 - 7 = -4, and n = 30. Plugging these values into the formula gives S_30 = 30/2 * (2*7 + (30-1)(-4)) = 15 * (14 - 116) = 15 * (-102) = -1530.

Use the Formula for the Sum of the First N