Question

The numbers of seats in the first 12 rows of a high-school auditorium form an arithmetic sequence. The first row has 9 seats. The second row has 11 seats.
Write a recursive formula to represent the sequence.
Write an explicit formula to represent the sequence.
How many seats are in the 12th row?
*I need the answer in normal form.*

Answer 1

Recursive formula:
a(n) = a(n-1) + 2, where a(1) = 9

Explicit formula:
a(n) = 7 + 2(n-1)

Number of seats in the 12th row:
a(12) = 7 + 2(12-1) = 7 + 2(11) = 7 + 22 = 29 seats