e , 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
inflection (Fig 6