I need help finding the nth term

Question

use the system of 2 equations in two variables a, and d, to write a formula for the general term (nth term) of the arithmetic sequence whose fourth term a is 17 and whose ninth term a, is 32

Answer 1

a4 = 17

a9 = 32

d= (32-17)/(9-4) = 15/5 = 3

a1 = 17-3(3) = 8

an =a1 + (n-1)(d)

an= 8 + (n-1)(3)

an = 8 +3n -3

an = 3n +5

a4 = 3(4)+5 = 17

a9 = 3(9)+5 =27+5 = 32