A series whose first two terms are -12 and -8, respectively, and whose last term is 124.

Answer 1

apparently the common difference is 4.

f(n) = -12 + (4)(n-1)

= -12 + 4n-4

= -16 + 4n

124 = -16 + 4n

140 = 4n

35 = n

The function is f(N) = 4n-16 for n=1,2,3,...,35