, if f ′(x) < 0 at every point sufficiently close to and to the left of c,
and f ′(x) > 0 at every point sufficiently close to and to the right of c,
then c is a point of local minima (iii) If f ′(x) does not change sign as x increases through c, then c is neither
a point of local maxima nor a point of local minima Infact, such a point
is called point of inflexion ® Second Derivative Test Let f be a function defined on an interval I and
c ∈ I