Answer
General Formula: $a_n=-70+(n-1)(-5)$
$a_{20}=-165$
Work Step by Step
The formula for the general term (the nth term) of an arithmetic sequence is:
$a_n=a_1+(n−1)d$
where
d = common difference
$a_1$ = first term
$a_n$ = nth term
n = term number
The given arithmetic sequence has:
$a_1=-70$ and $d=-5$
Substitute these into the given formula above:
$a_n = -70+ (n-1)(-5)$
Thus,
$a_{20} = -70+(20-1)(-5)
\\a_{20}=-70+19(-5)
\\a_{20}=-70+(-95)
\\a_{20}=-165$
