Exercise 51 Page 280

To find certain terms in a sequence described by an explicit formula, substitute the number of the desired term into the given formula to get the term's value. We can find the $\text{second},$ $\text{fourth},$ and $\text{eleventh}$ terms of the sequence by substituting $2,$ $4,$ and $11$ for $n$ into the above formula. Now, let's do the same thing for the $\text{fourth}$ and $\text{eleventh}$ terms.

$n^{\text{th}}$ term	$\text{-}7+(n-1)(5)$	$A(n)$
$2$	$\text{-}7+(2-1)(5)$	$\text{-}2$
$4$	$\text{-}7+(4-1)(5)$	$8$
$11$	$\text{-}7+(11-1)(5)$	$43$

The second, fourth, and eleventh terms are $\text{-}2,$ $8,$ and $43.$