Alternatively, if f ′(x) ≥ 0 for each x in (a, b)
(b) decreasing on (a,b) if
x1 < x2  in (a, b) ⇒ f (x1) > f (x2) for all x1, x2 ∈ (a, b) (c) constant in (a, b), if f (x) = c for all x ∈ (a, b), where c is a constant ® A point c in the domain of a function f at which either f ′(c) = 0 or f is not
differentiable is called a critical point of f ® First Derivative Test Let f  be a function defined on an open interval I