2.1: 15, 21, 29
2.2: 11, 13, 19 (hw), 21 (hw), 25, 37, 49
2.3: 3, 11, 33, 35
3.1: 7, 9
3.2: 23, 26 (answer: b = c = 0)
3.3: 1, 3, 49, 53, 55

(hw) — the problem is from the homework