Math Problem Statement

Find two positive numbers that satisfy the given requirements: The product is 192 and the sum of the first plus three times the second is a minimum.

Solution

The problem asks to find two positive numbers whose product is 192, and where the sum of the first number plus three times the second number is minimized.

Let's call the two numbers xx and yy.

Step 1: Define the relationship

We know: xy=192x \cdot y = 192 This gives us the equation: y=192xy = \frac{192}{x}

Step 2: Set up the function to minimize

We are asked to minimize the sum of the first number plus three times the second. This gives us the function: S(x,y)=x+3yS(x, y) = x + 3y Substituting y=192xy = \frac{192}{x} into this equation, we get: S(x)=x+3(192x)=x+576xS(x) = x + 3\left(\frac{192}{x}\right) = x + \frac{576}{x}

Step 3: Minimize the function

To find the value of xx that minimizes this function, we take the derivative of S(x)S(x) with respect to xx and set it equal to zero: S(x)=1576x2S'(x) = 1 - \frac{576}{x^2} Setting the derivative equal to zero to find the critical points: 1576x2=01 - \frac{576}{x^2} = 0 x2=576x^2 = 576 x=576=24x = \sqrt{576} = 24

Step 4: Find the corresponding yy

Since x=24x = 24, we can find yy using the equation xy=192x \cdot y = 192: 24y=192y=19224=824 \cdot y = 192 \quad \Rightarrow \quad y = \frac{192}{24} = 8

Conclusion:

The two numbers are 24\mathbf{24} and 8\mathbf{8}.

Would you like a more detailed breakdown of the steps? Here are some related questions:

  1. What if the product was a different number, like 150? How would the method change?
  2. How do you check if the result really minimizes the sum?
  3. Can we use graphical methods to find the minimum instead of calculus?
  4. Why do we take the derivative to find minimum values?
  5. What happens if we change the second number's coefficient (currently 3) to another number?

Tip: When minimizing or maximizing a function, always check if you are working with constraints, as it can affect your result.

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Math Problem Analysis

Mathematical Concepts

Optimization
Derivatives
Algebra

Formulas

x * y = 192
S(x) = x + 3 * (192 / x)
Derivative of S(x): S'(x) = 1 - (576 / x^2)

Theorems

Critical Points Theorem
Optimization using Derivatives

Suitable Grade Level

Grades 10-12