Find a formula for $a _ { n }$ for the arithmetic sequence.
$$a _ { 3 } = 19 , a _ { 13 } = 99$$
A) $a _ { n } = 3 + 8 n$
B) $a _ { n } = 5 + 3 n$
C) $a _ { n } = 8 + 3 n$
D) $a _ { n } = 3 ( 8 ) ^ { n }$
E) $a _ { n } = - 5 + 8 n$

Question

Quizplus · Accepted Answer

The common difference $d$ is $\frac{99 - 19}{13 - 3} = 8$. Using the formula $a_n = a_1 + (n-1)d$, we find $a_1 = -5$. Thus, $a_n = -5 + 8n$.

Find a Formula For ana _ { n }an​ For the Arithmetic Sequence

Find a Formula For $a _ { n }$ For the Arithmetic Sequence