There is no answer in my textbook for this question.
Please show a step by step solution so I could follow through...
Here's what I've done so far:
You know that derivatives essentially represent the slopes of a function. So, if you were to have tangents with a negative slope, f'(x) must be negative.
If f(x) does not have any negative tangents, that must mean f'(x) is never less than 0. Does this happen in your expression for f'(x)?
OT: When you're finding the x values to substitute in the original equation, do you solve for the numerator or denominator?