The problem is:
Expand the given function using Taylor's expansion around $a=1$.
$f(x)=(5x-4)^{-7/3}$, and then find the radius of convergence of the obtained series.
Hint : Write the nth derivative in the summation notation.
I've found a few derivatives but I don't know how to write the nth one, especially in the summation notation. Could you please help me solve this problem, I would be very grateful.