The formula for the sum of the first n terms of an arithmetic sequence is _______.
A) $\frac { n \left( a _ { 1 } - a _ { n } \right) } { 2 }$
B) $\frac { n \left( a _ { 1 } + a _ { n - 1 } \right) } { 2 }$
C) $a _ { 1 } + ( n - 1 ) d$
D) $\frac { n \left( a _ { 1 } + a _ { n } \right) } { 2 }$

Question

Quizplus · Accepted Answer

The correct formula for the sum of the first n terms of an arithmetic sequence is given by $S_n = \frac { n \left( a _ { 1 } + a _ { n } \right) } { 2 }$, where $S_n$ is the sum of the first n terms, $a_1$ is the first term, $a_n$ is the nth term, and n is the number of terms.

The Formula for the Sum of the First N Terms n(a1−an)2\frac { n \left( a _ { 1 } - a _ { n } \right) } { 2 }2n(a1​−an​)​

The Formula for the Sum of the First N Terms $\frac { n \left( a _ { 1 } - a _ { n } \right) } { 2 }$