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**Srengam** Hi all,

I have started reading Calculus Made Easy by Silvanus P.Thompson and am having a little difficulty early in.

The problem is

$\displaystyle y=\sqrt[q]{x^{3}}$

and I have $\displaystyle \frac{dy}{dx}=\frac{3}{q}x^{\frac{3}{q}-1}$

but the solution is $\displaystyle \frac{3}{q}x^{\frac{3-q}{q}}$

My workings are

$\displaystyle y=\sqrt[q]{x^{3}}=x^{\frac{3}{q}}, \frac{dy}{dx}=\frac{3}{q}x^{\frac{3}{q}-1}$

I thought that during the differentiation the index is reduced by 1?

Any help would be great,

thanks.