Math Problem Statement

Untuk x bilangan real, berapakah nilai terkecil dari 2^x + 3^x + 4^x + 5^x + 2018 + 2^(-x) + 3^(-x) + 4^(-x) + 5^(-x)?

Solution

The image contains a mathematical expression written in Indonesian, asking for the minimum value of the following function for real numbers xx:

2x+3x+4x+5x+2018+2x+3x+4x+5x2^x + 3^x + 4^x + 5^x + 2018 + 2^{-x} + 3^{-x} + 4^{-x} + 5^{-x}

Steps to solve this problem:

  1. Break the expression into two parts: The given expression can be split into two groups:

    • f1(x)=2x+3x+4x+5xf_1(x) = 2^x + 3^x + 4^x + 5^x
    • f2(x)=2x+3x+4x+5xf_2(x) = 2^{-x} + 3^{-x} + 4^{-x} + 5^{-x}

    Thus, the total expression is:

    f(x)=f1(x)+f2(x)+2018f(x) = f_1(x) + f_2(x) + 2018

  2. Symmetry analysis:

    • The terms 2x+2x,3x+3x,4x+4x,5x+5x2^x + 2^{-x}, 3^x + 3^{-x}, 4^x + 4^{-x}, 5^x + 5^{-x} are of the form ax+axa^x + a^{-x}.
    • Each of these terms achieves a minimum when x=0x = 0, as ax+ax2a^x + a^{-x} \geq 2 (by the AM-GM inequality).
  3. Evaluate at x=0x = 0: When x=0x = 0, each term simplifies as follows:

    f(0)=20+30+40+50+2018+20+30+40+50f(0) = 2^0 + 3^0 + 4^0 + 5^0 + 2018 + 2^0 + 3^0 + 4^0 + 5^0

    Since a0=1a^0 = 1 for any aa, this becomes:

    f(0)=1+1+1+1+2018+1+1+1+1=2028f(0) = 1 + 1 + 1 + 1 + 2018 + 1 + 1 + 1 + 1 = 2028

  4. Conclusion: The minimum value of the function occurs at x=0x = 0, and the value is 20282028.

Would you like further details or clarifications?

5 Related Questions:

  1. How do we prove that the function is minimized at x=0x = 0?
  2. What are the applications of the AM-GM inequality in other types of problems?
  3. How would this problem change if the constants were different, say 6x6^x or 7x7^x?
  4. How can we solve similar minimization problems using derivatives?
  5. What would happen if the constant 20182018 were replaced by a variable cc?

Tip: Always check if a function is symmetric or has certain properties like convexity when looking for its minimum or maximum values.

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Math Problem Analysis

Mathematical Concepts

Exponential Functions
Symmetry in Functions
AM-GM Inequality

Formulas

a^x + a^{-x} \geq 2

Theorems

Arithmetic Mean-Geometric Mean (AM-GM) Inequality

Suitable Grade Level

Grades 10-12