I'm working a location based home pricing model and I have a regression which looks like this:
where $x_1$ is longitude and $x_2$ is latitude.
I'm finding statistical significance in longitude, longitude squared and latitude squared but not in regular latitude itself. I know that in economic theory quadratic terms are used to capture the effect of diminishing returns, but in this case I find it odd that the quadratic is significant but the regular variable isn't.
How do I interpret these results?