Math Problem Statement

Use lhopital rule and show me its indeterminate form

Use L'Hopital's Rule and show me its indeterminate form

Solution

Let's analyze and solve the given limit using L'Hopital's Rule step by step.

The problem is:

limxln(2x)+5x22x1.\lim_{x \to \infty} \frac{\ln(2x) + 5x^2}{2^x - 1}.


Step 1: Check for the indeterminate form

  • As xx \to \infty:
    • ln(2x)+5x2\ln(2x) + 5x^2 \to \infty because 5x25x^2 \to \infty.
    • 2x12^x - 1 \to \infty because 2x2^x \to \infty.
  • Thus, the limit is in the form \frac{\infty}{\infty}, which allows the application of L'Hopital's Rule.

Step 2: Apply L'Hopital's Rule

Differentiate the numerator and denominator with respect to xx:

  1. Numerator:
    ddx(ln(2x)+5x2)=12x2+10x=1x+10x.\frac{d}{dx} \left( \ln(2x) + 5x^2 \right) = \frac{1}{2x} \cdot 2 + 10x = \frac{1}{x} + 10x.

  2. Denominator:
    ddx(2x1)=ln(2)2x.\frac{d}{dx} \left( 2^x - 1 \right) = \ln(2) \cdot 2^x.

Thus, the new limit becomes: limx1x+10xln(2)2x.\lim_{x \to \infty} \frac{\frac{1}{x} + 10x}{\ln(2) \cdot 2^x}.


Step 3: Simplify and check indeterminate form

As xx \to \infty:

  • The term 1x0\frac{1}{x} \to 0, so the numerator simplifies to 10x10x.
  • The denominator grows exponentially as ln(2)2x\ln(2) \cdot 2^x.

The new limit is still in the form \frac{\infty}{\infty}, so we apply L'Hopital's Rule again.


Step 4: Apply L'Hopital's Rule again

Differentiate the numerator and denominator again:

  1. Numerator:
    ddx(10x)=10.\frac{d}{dx} \left( 10x \right) = 10.

  2. Denominator:
    ddx(ln(2)2x)=ln(2)ln(2)2x=(ln(2))22x.\frac{d}{dx} \left( \ln(2) \cdot 2^x \right) = \ln(2) \cdot \ln(2) \cdot 2^x = (\ln(2))^2 \cdot 2^x.

Thus, the new limit becomes: limx10(ln(2))22x.\lim_{x \to \infty} \frac{10}{(\ln(2))^2 \cdot 2^x}.


Step 5: Evaluate the final limit

  • As xx \to \infty, the denominator (ln(2))22x(\ln(2))^2 \cdot 2^x \to \infty.
  • Thus, the entire fraction approaches: 10=0.\frac{10}{\infty} = 0.

Final Answer:

[ \lim_{x \to \infty} \frac{\ln(2x) + 5x

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Math Problem Analysis

Mathematical Concepts

Limits
Indeterminate Forms
Exponential Growth
Logarithmic Functions

Formulas

L'Hopital's Rule: lim (f(x)/g(x)) = lim (f'(x)/g'(x)) when f(x) and g(x) approach ∞ or 0

Theorems

L'Hopital's Rule

Suitable Grade Level

Grades 11-12