Answer
$a_n = 9 + 4(n-1)$
$a_{10} = 45$
Work Step by Step
RECALL:
The $n^{th}$ term $a_n$ of an arithmetic sequence can be found using the formula:
$a_n = a + d(n-1)$
where
$a$ = first term
$d$ = common difference
$n$ = term number
The given arithmetic sequence has $a=9$ and $d=4$.
This means that the $n^{th}$ term of the sequence is given by the formula:
$a_n = 9 + 4(n-1)$
Thus, the 10th term of the sequence is:
$a_{10} = 9+4(10-1)
\\a_{10}=9+4(9)
\\a_{10} = 9+36
\\a_{10} = 45$