Find the sum of the first n terms of the following arithmetic sequence.
-$$a _ { 1 } = 1 , d = - 1 ; \quad n = 6$$
A) 6
B) -7
C) $- 5$
D) $- 9$

Question

Quizplus · Accepted Answer

The sum of the first n terms of an arithmetic sequence is given by the formula $ S_n = \frac{n}{2} (2a_1 + (n-1)d) $. Substituting the given values: $ S_6 = \frac{6}{2} (2 \times 1 + (6-1)(-1)) = 3(2 - 5) = 3(-3) = -9 $.

Find the Sum of the First N Terms of the Following