Answer
An equation for the $n^{th}$ term is
$a_n=n+3$
and
$a_{25}=28$
Work Step by Step
The given arithmetic sequence is
$4,5,6,7,...$
The first term $a_1=4,$
and the common difference is $d=5-4=1$
The $n^{th}$ term formula is
$\Rightarrow a_n=a_1+(n-1)d$
Substitute $4$ for $a_1$ and $1$ for $d$.
$\Rightarrow a_n=4+(n-1)1$
Simplify.
$\Rightarrow a_n=4+n-1$
$\Rightarrow a_n=n+3$
Substitute $25$ for $n$.
$\Rightarrow a_{25}=25+3$
Simplify.
$\Rightarrow a_{25}=28$.
