Categories Ask Mathematics Having trouble to prove this divisibility. Post author By Q+A Expert Post date March 30, 2020 No Comments on Having trouble to prove this divisibility. Lets suppose a ≥ 1. Prove that if a | s + 3 & a | s + 7 then a = 1, 2 or 4. Tags 2 or 4., Lets suppose a ≥ 1. Prove that if a | s + 3 & a | s + 7 then a = 1