Math Problem Statement

n!>2 n for alln≥4

Solution

The inequality n!>2nn! > 2^n holds for n4n \geq 4. To verify this, let's check a few values manually first and then generalize the result.

  1. For n=4n = 4: 4!=4×3×2×1=244! = 4 \times 3 \times 2 \times 1 = 24 24=162^4 = 16 So, 4!=24>16=244! = 24 > 16 = 2^4.

  2. For n=5n = 5: 5!=5×4×3×2×1=1205! = 5 \times 4 \times 3 \times 2 \times 1 = 120 25=322^5 = 32 So, 5!=120>32=255! = 120 > 32 = 2^5.

  3. For n=6n = 6: 6!=6×5×4×3×2×1=7206! = 6 \times 5 \times 4 \times 3 \times 2 \times 1 = 720 26=642^6 = 64 So, 6!=720>64=266! = 720 > 64 = 2^6.

As you can see, starting from n=4n = 4, the factorial function grows much faster than the exponential function 2n2^n. Therefore, the inequality n!>2nn! > 2^n holds for all n4n \geq 4.

Summary:

For all n4n \geq 4, n!>2nn! > 2^n.


Do you want more details or have any questions?

Here are 5 related questions to deepen your understanding:

  1. How can we rigorously prove that n!>2nn! > 2^n for all n4n \geq 4?
  2. What is the asymptotic behavior of factorial and exponential functions as nn \to \infty?
  3. How does Stirling’s approximation help in comparing n!n! and 2n2^n?
  4. Can you find another inequality involving n!n! and a different exponential function?
  5. How does the factorial growth compare with other common functions like polynomials or logarithms?

Tip: Factorial functions grow extremely fast compared to exponential functions, making them useful for analyzing large combinatorial problems.

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Math Problem Analysis

Mathematical Concepts

Inequalities
Factorials
Exponential Functions

Formulas

n! > 2^n

Theorems

Factorial Growth
Comparison of Factorial and Exponential Growth

Suitable Grade Level

Grades 10-12