What is the derived function for f(x) = k /((1+x/12)^n)



Hi, it has been a while since I done some differentiation and a little
help would be appreciated.

The function is f(x) = k /((1+x/12)^n)
Where k is a constant value and n = 0 -> infinity

What is the derived function for f(x):
f'(x) = -n*k*(1+x/12)^(-n-1)

.