My OLS regression looks like this:
I do not include $x_3$ linear because it vifs with squared value and without squared value I have wrong specification according to RESET.
How do I interpret the $\beta_3$ in my equation (in general)? I know it should be something like: $$\Delta y=(2\beta_3x_3)\Delta x$$ But what should I use as an $x_3$? Should it be an average $x_3$ value?