Răspuns:
(a, b) = 7
[a, b] = 84
a × b = (a, b) × [a, b]
a × b = 7 × 84
a × b = 588
(a, b) = 7
a = 7n
b = 7m
(n, m) = 1 (sunt prime între ele)
7n × 7m = 588
49 × n × m = 588
n × m = 588 ÷ 49
n × m = 12
(n, m) ∈ {(1, 12); (12, 1); (3, 4); (4, 3)} / × 7
(a, b) ∈ {(7, 84); (84, 7); (21, 28); (28, 21)}