2) Write a formula for the nth term of each arithmetic sequence. Then use the formula to find a15.?

a. 3, 8, 13, 18
b. a1 = –3 and d = 6

1 Answer

a_15=81

Explanation:

formula for nth term is
a_n= a_1+(n-1)d

a)
nth term is
a_n=3+(n-1)5
[from given series a=3, d=5]

b)
given a_1=-3, d=6 so

a_n= -3+(n-1)6

a_15=-3+(15-1)6

a_15=-3+84

a_15=81