1. The problem statement, all variables and given/known data Dear Mentors and PF helpers, Please help me to understand this question. Thank you for your time. 2. Relevant equations My understanding of a one-one function is that if a horizontal line where to intersect the curve, there should be only 1 intersection. 3. The attempt at a solution 1) My questions is what does "the largest possible" domain means? Does it mean to find the widest interval between the lower limit and the higher limit? Or does it mean that the upper limit should be as great as possible?