Consider f(x) = 2x2 , ∀ x ∈ R
From the graph, we have f(x) = 0 if x = 0 and f(x) ≥ 0 ∀ x ∈ R
The minimum value of f is 0 and the point of minimum value of f is x = 0.
The graph of function f has no maximum value, and hence, no point of maximum value of f in R.
Let f be a function defined on an open interval D. Let f be continuous at a critical point, a, in D.
Local minima
If f '(x) changes its sign from negative to positive as x increases through a, i.e. if f '(x) < 0 at every point sufficiently close to and to the left of a, and f '(x) > 0 at every point sufficiently close to and to the right of a, then "a" is the point of local minima.
The local minimum value is f(a).
Local maxima
If f '(x) changes its sign from positive to negative as x increases through a, i.e. if f '(x) > 0 at every point sufficiently close to and to the left of a, and f '(x) < 0 at every point sufficiently close to and to the right of a, then a is the point of local maxima.
The local maximum value is f(a).
'0' is neither a point of local maxima nor a point of local minima.
'0' is the point of inflection.
Point of inflection
If f '(x) does not change its sign as x increases through critical point "a", then "a" is known as the point of inflection.
At point "a", f has neither a point of local maxima nor a point of local minima.
Steps for finding local maxima and local minima:
Step1: Find the derivative of f(x), i.e. f '(x).
Step2: Let a1,a2,a3,... ... ..., an be the roots of f '(x) = 0 . Here, a1,a2,a3,... ... ..., an are called the critical points or stationary points of x.
Note: The local maxima or local minima of f(x) can be attained at some or all these stationary points of x.
Step 3:Consider x = a1. If f '(x) > 0 at the left neighbourhood values of a1 and if f '(x) < 0 at the right neighbourhood values of a1 , then x = a1 is the point of local maxima.
Consider x = a1. If f '(x) < 0 at the left neighbourhood values of a1 and if f '(x) > 0 at the right neighbourhood values of a1, then x = a1 is the point of local minima.
Note: If f '(x) does not change its sign as x increases through a1 , then x = a1 is neither a point of local maxima nor a point of local minima.
Consider f(x) = 2x2 , ∀ x ∈ R
From the graph, we have f(x) = 0 if x = 0 and f(x) ≥ 0 ∀ x ∈ R
The minimum value of f is 0 and the point of minimum value of f is x = 0.
The graph of function f has no maximum value, and hence, no point of maximum value of f in R.
Let f be a function defined on an open interval D. Let f be continuous at a critical point, a, in D.
Local minima
If f '(x) changes its sign from negative to positive as x increases through a, i.e. if f '(x) < 0 at every point sufficiently close to and to the left of a, and f '(x) > 0 at every point sufficiently close to and to the right of a, then "a" is the point of local minima.
The local minimum value is f(a).
Local maxima
If f '(x) changes its sign from positive to negative as x increases through a, i.e. if f '(x) > 0 at every point sufficiently close to and to the left of a, and f '(x) < 0 at every point sufficiently close to and to the right of a, then a is the point of local maxima.
The local maximum value is f(a).
'0' is neither a point of local maxima nor a point of local minima.
'0' is the point of inflection.
Point of inflection
If f '(x) does not change its sign as x increases through critical point "a", then "a" is known as the point of inflection.
At point "a", f has neither a point of local maxima nor a point of local minima.
Steps for finding local maxima and local minima:
Step1: Find the derivative of f(x), i.e. f '(x).
Step2: Let a1,a2,a3,... ... ..., an be the roots of f '(x) = 0 . Here, a1,a2,a3,... ... ..., an are called the critical points or stationary points of x.
Note: The local maxima or local minima of f(x) can be attained at some or all these stationary points of x.
Step 3:Consider x = a1. If f '(x) > 0 at the left neighbourhood values of a1 and if f '(x) < 0 at the right neighbourhood values of a1 , then x = a1 is the point of local maxima.
Consider x = a1. If f '(x) < 0 at the left neighbourhood values of a1 and if f '(x) > 0 at the right neighbourhood values of a1, then x = a1 is the point of local minima.
Note: If f '(x) does not change its sign as x increases through a1 , then x = a1 is neither a point of local maxima nor a point of local minima.