Write the first 4 terms of each sequence.
a. u1 = 20
un = un-1 + 6 where n ≥ 2
b. u1 = 47
un = un-1- 3 where n ≥ 2
c. u0 = 32
un = 1.5 · un-1 where n ≥ 1
d. u1 = -18
un = un-1 + 4.3 where n ≥ 2