I am working through the book Applied Predictive Modeling and came across something that was a bit confusing.
It discussed adding non linearity to a model to improve its fit - I get this part.
For example: $x^2 + 2x - 4$
What is the interpretation of these values though?
When we are using just a normal linear regression or a multivariate regression, we would say that the coefficients like 2 would suggest its relative importance relative to the other features being included in the model. However, what does this mean in the context of quadratic functions?
ie. Fuel efficiency of a car based on 2 Displacement + Displacement$^2$ -4
What exactly does displacement squared mean?
Any help would be greatly appreciated.