Non linear regression

Iam doing nonlinear regression to the function y=a*x^n/(x^n+b^n) where i have 9 values of x and corresponding values of y. How do i go about doing the nonlinear regression and find the constants a,b and n?..i have not been able to understand nlinfit or lsqcurvefit..pls help me thanks

[Robert Cumming]

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