How to Minimize the Sum of Squares of Three Numbers That Add Up to 12?

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SUMMARY

The problem involves finding three positive numbers, x, y, and z, that sum to 12 while minimizing the sum of their squares, represented by the function f(x, y, z) = x² + y² + z². The key insight is to express z in terms of x and y using the equation x + y + z = 12, which simplifies the problem to a two-dimensional optimization task. This approach leverages concepts from calculus, specifically partial derivatives, to identify the minimum value of the function.

PREREQUISITES
  • Understanding of partial derivatives
  • Familiarity with optimization techniques in calculus
  • Basic knowledge of algebraic manipulation
  • Ability to solve equations involving multiple variables
NEXT STEPS
  • Study optimization problems involving multiple variables using partial derivatives
  • Learn about Lagrange multipliers for constrained optimization
  • Explore the method of substitution in algebra to simplify equations
  • Practice solving similar problems in calculus involving minimization and maximization
USEFUL FOR

Students studying calculus, particularly those focusing on optimization problems, as well as educators looking for examples of applying partial derivatives in real-world scenarios.

ScienceGeek24
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Homework Statement



Find three positive numbers whose sum is 12 and the sum of whose squares is as small as possible.

Homework Equations


The Attempt at a Solution



I don;t even know how to start this one, this is a section from partial derivatives on the max and mins. Please i need guidance through this exercise. Thank you!
 
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Hi ScienceGeek24! :smile:

Start by calling the three numbers x y and z, and putting f(x,y,z) = x2 + y2 + z2 :wink:
 
In addition to tiny-tim's good first idea, how about using the fact that you know that x+y+z=12, so you know what z is in terms of x and y - then you only have a 2D problem to solve.
 

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