(c)
f`(x) > 0 needed, or f`(x) ≥ 0, or “as x increases, f(x) increases”
f`(x) = (x − 1/x)^2, > 0 always, or ≥ 0 always
Is the answer to the following question:
f ′(x) = x^2 – 2 + x^(-2).
c) Prove that f is an increasing function.
I understand the first line of the answer, that the gradient has to be > 0, but I don't understand the proof part (line 2). Could someone explain how to prove it please?