Answer
Formula for $a_{n}$ term of the given sequence = $a_{1}$ + (n - 1) d.
Where
$a_{1}$ = The first term
d = Common difference
n = $n^{th}$ number of term
Given
$a_{1}$, the first term = (-20)
Common difference (d) = (-4)
$20^{th}$ term of sequence = -96
Work Step by Step
Formula for $a_{n}$ term of the given sequence = $a_{1}$ + (n - 1) d.
Where
$a_{1}$ = The first term
d = Common difference
n = $n^{th}$ number of term
Given
$a_{1}$, the first term = (-20)
Common difference (d) = (-4)
$20^{th}$ term of sequence = -20 + (20 - 1) $\times$ (-4)
= -20 + 19$\times$(-4)
= -20 -76
= -96
