3)
f(n) = 4 x 1 + 5 = 9
f(n) = 4 x 2 + 5 = 13
f(n) = 4 x 3 + 5 = 17
f(n) = 4 x 4 + 5 = 21
4)
f(n) = 3(1-2) - 4 = -7
f(n) = 3(2-2) - 4 = -4
f(n) = 3(3-2) - 4 = -1
f(n) = 3(4-2) - 4 = 2
5)
f(n) = 3n - 4
n = 17
