Given a set of data points, say X={...} and Y={...}, how do I use the Least Squares operation (or another operation if necessary) to fit the curve y=a*x^b to the data points and find the constants a and b. Any help is appreciated. Here is what I have tried:

with(CurveFitting):

LeastSquares([X,Y],v,curve=a*x^b);

And I get an error that the curve is not linear. Help please.