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.

A. Write a recursive formula to represent the sequence.
B. Write an explicit formula to represent the sequence.
C. How many seats are in the 12th row?

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. 

A. Write a recursive formula to represent the sequence.
B. Write an explicit formula to represent the sequence. 
C. How many seats are in the 12th row?

anonymous · Answer

A) an=a1+(n-1)d
B) an=2n+7
C) 31