Math Problem Statement

Can you proof that eln(x)n1ln(x)neln(x)n\frac{e^{\frac{\ln\left(x\right)}{n}}-1}{\frac{\ln\left(x\right)}{n}}\le e^{\frac{\ln\left(x\right)}{n}}

Solution

We aim to prove the inequality:

eln(x)n1ln(x)neln(x)n\frac{e^{\frac{\ln(x)}{n}} - 1}{\frac{\ln(x)}{n}} \leq e^{\frac{\ln(x)}{n}}

Step 1: Define the variable

Let z=ln(x)nz = \frac{\ln(x)}{n}. Substituting zz into the inequality, it becomes:

ez1zez\frac{e^z - 1}{z} \leq e^z

where z0z \neq 0 (since division by zero is undefined). Now, we analyze this inequality.


Step 2: Rewrite the inequality

Multiply through by zz, assuming z>0z > 0 (if z<0z < 0, we'll analyze separately):

ez1zez.e^z - 1 \leq z e^z.

Rearranging terms:

ezzez10.e^z - z e^z - 1 \leq 0.

Factoring eze^z out from the terms where possible:

ez(1z)10.e^z (1 - z) - 1 \leq 0.


Step 3: Analyze f(z)=ez(1z)1f(z) = e^z (1 - z) - 1

Let f(z)=ez(1z)1f(z) = e^z (1 - z) - 1. We will determine whether f(z)0f(z) \leq 0 for all zz.

  1. Compute f(0)f(0):

    f(0)=e0(10)1=0.f(0) = e^0 (1 - 0) - 1 = 0.

  2. Compute the derivative f(z)f'(z):

    Using the product rule:

    f(z)=ddz(ez(1z))=ez(1z)+ez(1)=ez(1z1).f'(z) = \frac{d}{dz} \left(e^z (1 - z)\right) = e^z (1 - z) + e^z (-1) = e^z (1 - z - 1).

    Simplifying:

    f(z)=zez.f'(z) = -z e^z.

  3. Analyze f(z)f'(z):

    • For z>0z > 0, f(z)=zez<0f'(z) = -z e^z < 0 (decreasing function).
    • For z<0z < 0, f(z)=zez>0f'(z) = -z e^z > 0 (increasing function).

    Thus, f(z)f(z) reaches a maximum at z=0z = 0, where f(0)=0f(0) = 0.


Step 4: Conclude

Since f(z)f(z) is decreasing for z>0z > 0 and increasing for z<0z < 0, with f(0)=0f(0) = 0, we have f(z)0f(z) \leq 0 for all zz. This implies:

ez(1z)10,e^z (1 - z) - 1 \leq 0,

or equivalently:

ez1zez.e^z - 1 \leq z e^z.

Dividing through by z>0z > 0 (or equivalently taking the limit as z0z \to 0), we confirm that:

ez1zez.\frac{e^z - 1}{z} \leq e^z.


Step 5: Original inequality

Returning to the original variables, z=ln(x)nz = \frac{\ln(x)}{n}, we conclude:

eln(x)n1ln(x)neln(x)n.\frac{e^{\frac{\ln(x)}{n}} - 1}{\frac{\ln(x)}{n}} \leq e^{\frac{\ln(x)}{n}}.

Summary

The inequality holds for all x>0x > 0 and n>0n > 0. Let me know if you want further clarification!


Relative Questions:

  1. Can you graph ez1z\frac{e^z - 1}{z} and eze^z to visualize their relationship?
  2. How does this proof rely on properties of the exponential function?
  3. What happens when z0z \to 0? Does the inequality still hold?
  4. How can this inequality be applied in real-world scenarios?
  5. Is there a similar inequality involving other transcendental functions?

Tip: For inequalities involving exponential or logarithmic functions, using derivatives to analyze monotonicity is often a powerful tool!

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Math Problem Analysis

Mathematical Concepts

Exponential Functions
Logarithmic Functions
Inequalities
Calculus (Derivatives)

Formulas

\( e^z \) expansion: \( \frac{e^z - 1}{z} \)
Derivative of \( f(z) = e^z (1 - z) \)

Theorems

Monotonicity of Functions
Exponential Function Properties

Suitable Grade Level

Undergraduate Mathematics (or Advanced High School Calculus)