# how to obtain solution of this bessel equation using Frobenius method

Given this equation:

$$\frac{1}{r}\frac{d}{dr}\bigg(r \frac{dT}{dr} \bigg) - \bigg(\frac{2h}{bk} \bigg)(T-T_a) = 0$$

I can let $$x=r\sqrt{(2h/bk)}$$ and $$z=T-T_a$$ to obtain the bessel equation using the appropriate substitutions

$$x^2 \frac{d^2z}{dx^2} + x \frac{dz}{dx} - x^2z = 0$$

To express the solution for $$z$$, I read that one technique is to use the Frobenius method, but I am not sure how to apply this to be Bessel function above... Any help ?