Question

Test whether the following functions are increasing or decreasing.

f(x) = x – 1/x, x ∈ R, x ≠ 0.

Answer 1

f(x) = x - 1/x

∴ f'(x) > 0 for all x ∈ R, where x ≠ 0 

∴ f is increasing for all x ∈ R, where x ≠ 0.