Find the derivative of the function
f(x)=ln((15x)/(x²+15))
a. f'(x)=(3)/(x)+(2x)/(x²+15)
b. f'(x)=(1)/(x)+(2x)/(x²+15)
c. f'(x)=(15-x²)/(x(x²+15))
d. f'(x)=(15)/(x)+(2x)/(x²+15)