We are given these two equalities AB + AC = 5 (1) AC + BC = 4 (2) Subtract (2) from (1) (both sides). The terms "AC" will annihilate, so we will get AB - BC = 5 - 4 = 1. (3) Due to triangle inequalities, | AB - BC | < AC for any triangle ABC. So, from (3) we conclude that 1 < AC, or AC > 1. ANSWER. From the given equalities, the triangle inequalities imply AC > 1.