Seats in a theater are set up as the following:
The first row has 8 seats, the seconds row has 12 seats, the third row has 18 seats, and the fourth row has 26 seats. How many seats are in the 7th row?
The "2nd difference" consists of an arithmetic sequence of 4, 6, 8, .... , so it can be expressed by
a quadratic function.
that would be term(n) = n^2 + n + 6
term(7) = 49 + 7 + 6 = 62
if you don't know how to find that function you could just continue the pattern:
term1 = 8
term2 = term1 + 4 = 12
term3 = term2 + 6 = 18
term4 = term3 + 8 = 26
term5 = term4 + 10 = 36
term6 = term5 + 12 = 48
term7 = term6 + 14 = 62 <----- same as value obtained from formula of function