Determine the interval on which The function is differentiable :

Question

f(x) = 3x - 5

Answer 1

I know that if f is differntiable on (a,infinity) and the one side limt f(x) -f(a) / x-a exists then its differntiable on [a,infinity)

I found the interval of the function which appears to be (infinty,infinity)
i.e R .. all real numbers

But i really cant find the interval of the derivtive !!!

Answer 2

You answered the question you asked, the function is differentiable for all real values of x

The derivative is the slope of that straight line, 3 , so 3 and only 3