I can use Excel's Data Analysis and Regression to fit my data to a linear equation:
y=a+b*x1+c*x2
where a,b,c are constants and x1 and x2 are two independent variables.

However, in my case, my data seems to indicate that I need this function instead:
y=a+b*x1+c*x2^p
Where p is raising x2 to some power constant.

Is it possible to use Excel to find the constants in this case?

I also came across the LINEST function, but I am not sure if that can be used as an alternative?
(what are the pros/cons between the two methods?)