I have such a function f(x) = (x-4)/(x+8), and I need to find the interval on which it is increasing:

I found the derivative f'(x) = [(x+8)-(x-4)]/(x+8)^2 = 12/(x^2 + 16x + 64), and for the denumerator the only critical point is -8, and the function is positive

on the both sides of (-8),

do I have to mention the f(x) is increasing on (-Inf, -8)U(-8, Inf) ?