#### Answer

If -83 is last term of $a_{n}$ then there are 22 terms in $a_{n}$.
= 22 terms

#### Work Step by Step

From graph
First term $a_{1}$ = 1
Second term $a_{2}$ = -3
Third term $a_{3}$ = -7
Sequence = 1, -3, -7, . . . . .
Common difference (d) = -7 + 3 = -3 - 1 = -4
Given last term ($a_{l}$)= -83
Number of terms = $\frac{Last term - first term }{d}$ + 1
= $\frac{a_{l} - a_{1}}{d}$ + 1
= $\frac{-83 - 1}{-4}$ + 1
= $\frac{-84}{-4}$ + 1
= 21 + 1
= 22
If -83 is last term of $a_{n}$ then there are 22 terms in $a_{n}$.