Math Problem Statement

A function f is defined as 2f(x) + 3f((2024/x)) = 5x, for all non-zero real numbers x. Then, f(8) is equal to

Solution

To solve for f(8)f(8), let's analyze the functional equation given:

2f(x)+3f(2024x)=5x2f(x) + 3f\left(\frac{2024}{x}\right) = 5x

Step 1: Substitute x=8x = 8

Let's first try substituting x=8x = 8 directly to see if it gives us useful information.

2f(8)+3f(20248)=582f(8) + 3f\left(\frac{2024}{8}\right) = 5 \cdot 8

Simplify the right side:

2f(8)+3f(253)=402f(8) + 3f(253) = 40

So we get one equation:

2f(8)+3f(253)=402f(8) + 3f(253) = 40

Step 2: Substitute x=253x = 253

Now, let's try substituting x=253x = 253 into the functional equation to get another relation.

2f(253)+3f(2024253)=52532f(253) + 3f\left(\frac{2024}{253}\right) = 5 \cdot 253

Calculate 52535 \cdot 253:

5253=12655 \cdot 253 = 1265

So, we have:

2f(253)+3f(8)=12652f(253) + 3f(8) = 1265

Step 3: Set up the system of equations

Now we have two equations:

  1. 2f(8)+3f(253)=402f(8) + 3f(253) = 40
  2. 3f(8)+2f(253)=12653f(8) + 2f(253) = 1265

This is a system of linear equations in f(8)f(8) and f(253)f(253).

Step 4: Solve the system of equations

Let's solve for f(8)f(8) and f(253)f(253) by using the elimination or substitution method.

Multiply the first equation by 3 and the second equation by 2 to align the coefficients of f(8)f(8):

6f(8)+9f(253)=1206f(8) + 9f(253) = 120 6f(8)+4f(253)=25306f(8) + 4f(253) = 2530

Now, subtract the first modified equation from the second:

(6f(8)+4f(253))(6f(8)+9f(253))=2530120(6f(8) + 4f(253)) - (6f(8) + 9f(253)) = 2530 - 120

5f(253)=2410-5f(253) = 2410

Divide by 5-5:

f(253)=482f(253) = -482

Step 5: Substitute back to find f(8)f(8)

Now substitute f(253)=482f(253) = -482 into the first equation:

2f(8)+3(482)=402f(8) + 3(-482) = 40

2f(8)1446=402f(8) - 1446 = 40

Add 1446 to both sides:

2f(8)=14862f(8) = 1486

Divide by 2:

f(8)=743f(8) = 743

Final Answer

f(8)=743f(8) = 743

Would you like further details on any steps or have any questions?


  1. How do functional equations generally work?
  2. What techniques help in solving systems of equations like this one?
  3. Are there alternative methods to solve functional equations?
  4. How can we verify the solution in such problems?
  5. Why did we choose x=8x = 8 and x=253x = 253 for substitution?

Tip: Solving functional equations often involves strategic substitutions to simplify the equation or reduce unknowns.

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Math Problem Analysis

Mathematical Concepts

Algebra
Functional Equations
Systems of Equations

Formulas

2f(x) + 3f(2024/x) = 5x

Theorems

Substitution Method for Solving Systems of Equations

Suitable Grade Level

Grades 11-12