Calculus Concavity and Derivative Tests

Question

Let f be the function defined by

f(x) = x + (9/x)

on (-infinity, 0)

Find the derivative of f.

choices:

1. (x^2 - 9)/(x^4)
2. (x^2 + 9)/(x^2)
3. (x^2 - 9)/(x)
4. (x^2 + 9)/(x)
5. (x^2 + 9)/(x^4)
6. (x^2 - 9)/(x^2)

Answer 1

f'(x) = 1 - (9/x²) ... and maybe this will help you to answer any other parts of the question which you have not submitted.