a) The recursive formula for the number of seats in the n th row will be;
S1 = 9
S(n) = S (n-1) +2
b) Explicit formula; is that of an arithmetic progression; such that if a is the first term , and d is the common difference , then the n th term will be given by the formula: a + (n-1) d; where a is 9, and d is 2
Hence; for n th row = 9+ 2(n-1)
c) Number of seats in 12 th row using the formula in b.
n = 12 , a = 9, d = 2
therefore; 9 + 2(12-1)
= 9 + 2(11)
= 31 seats
