Investigation of functions for local extrema.
Investigation of functions for local extrema.
An extremum refers to a maximum or minimum of a function.
Necessary condition for an extremum.
If the differentiable function
Points where conditions (1) are satisfied are called stationary points of the function
Sufficient conditions for extrema of a function of two variables.
Let
Let
Then:
a) If
b) If
c) If
Examples.
Find the extrema of functions of two variables:
7.187.
Solution.
Let's find the first-order partial derivatives of the function
Next, we find the stationary points by setting the found derivatives to zero and solving the system:
Thus, we have found the stationary point
Next, we find
Since
Answer: The function has a minimum at point
7.189.
Solution.
Let's find the first-order partial derivatives of the function
Next, we find the stationary points by setting the found derivatives to zero and solving the system:
Thus, we have two stationary points
Next, we find
Since
Since
Answer: The function has a minimum at point
7.193.
Solution.
Let's find the first-order partial derivatives of the function
Next, we find the stationary points by setting the found derivatives to zero and solving the system:
From here, we find four stationary points:
Next, we find
Since
At point
Answer: The function has a minimum at point
Tags: Investigation of functions, Necessary condition for an extremum, calculus, extremum, local extrema, mathematical analysis