199k views
2 votes
Find the maximum and minimum values of the function f(x, y, z) = x²y²z² subject to the constraint x² + y² + z² = 169. The maximum value is _______occurs at points _____.

User Vezult
by
7.3k points

1 Answer

4 votes

Final answer:

The maximum value of the function f(x, y, z) = x²y²z² subject to the constraint x² + y² + z² = 169 occurs when x, y, and z are equal due to the symmetry of the problem. The maximum point occurs at x = y = z = √(169/3). There is no minimum value on the sphere since the function approaches zero as any variable approaches zero.

Step-by-step explanation:

The student has asked to find the maximum and minimum values of the function f(x, y, z) = x²y²z² subject to the constraint x² + y² + z² = 169. To find these extremum points, one must use a method such as Lagrange multipliers, which is a strategy for finding the local maxima and minima of a function subject to equality constraints.

We set up the Lagrange function L(x, y, z, λ) = x²y²z² - λ(x² + y² + z² - 169). Taking partial derivatives and setting them to zero will give us a system of equations that we can solve for the variables and lambda.

However, based on the spherical symmetry of the constraint and the objective function, we can infer that the maximum value will occur when x = y = z. Substituting z = √(169 - x² - y²) into the objective function and differentiating will let us find the extremum points.

The maximum value of the function occurs at the points where x, y, and z are equal because the geometric mean is less than or equal to the arithmetic mean. As such, the maximum will occur at the point where x = y = z = √(169/3), since the constraint dictates that the sum of their squares is 169. The function f(x, y, z) does not have a minimum in this context as it approaches zero when any of the variables approach zero, under the constraint. The global minimum is zero, but it occurs when one or more variables are zero which is not a point on the sphere defined by the constraint x² + y² + z² = 169.

User Pradeep Bhadani
by
8.2k points