Rule #1 - Be VERY careful with models that don't have inverses. This can lead to multiple, confusing solutions.
Rule #2 - The quadratic model is popular, due to its simplicity, but you MUST be careful to restrict its Domain.
Rule #3 - Speak and write with clarity. "The Quadratic Model" is insufficient. What quadratic model. I'm certain Ii could dream up a few thousand that would be entirely inappropriate.
Where does that leave us?