(i) Define an arithmetic progression and a geometric progression.
(ii) For each of the following sequences, state whether it is an arithmetic progression, a geometric progression or neither:
(a) 7, 11, 15, 19, \dots
(b) 4, \,-12,\, 36, \,-108, \dots
(c) 5, 9, 14, 20, \dots
(iii) For every sequence in part (ii) that is a progression, write down the value of the common difference or the common ratio and give one reason for your choice.
(a) 7, 11, 15, 19, …
(b) 4, −12, 36, −108, …
(c) 5, 9, 14, 20, …