Fit predetermined curve to data set I have a set of $5$ data points $(x, y)$. I need to find two constants ($a$ and $b$), so that the curve $x\cdot y^a=b$ fits my data set. The question states that I can find the constants from the fitting process. However, I'm not sure where to start. Which method do I use to do this? Thanks for any help.

Applying the natural logarithm to your curve, we have $$ \ln x + a \ln y = \ln b.$$ This shows a linear relationship between $\ln x$ and $\ln y$.

Take your data points $(x,y)$ and convert them to new points $(\ln x, \ln y)$ by applying the natural logarithm. Take this set of converted data points and find the line of best fit. Apply the exponential function to your line to get the curve you seek.