Math Problem Statement

Evaluate the limit using L'Hospital's rule if necessary: lim (x → ∞) (x^14 / e^x).

Solution

The problem asks to evaluate the following limit:

limxx14ex\lim_{x \to \infty} \frac{x^{14}}{e^x}

We can attempt to solve this problem using L'Hôpital's Rule since both the numerator and denominator approach infinity as xx approaches infinity. L'Hôpital's Rule states that if we encounter an indeterminate form \frac{\infty}{\infty}, we can differentiate the numerator and denominator and then take the limit of the resulting expression.

Step 1: Check the form

The given expression is of the indeterminate form \frac{\infty}{\infty} as xx \to \infty, so we can apply L'Hôpital's Rule.

Step 2: Apply L'Hôpital's Rule

We will differentiate the numerator and denominator:

  • Derivative of the numerator x14x^{14} is 14x1314x^{13}.
  • Derivative of the denominator exe^x is exe^x.

Thus, the limit becomes:

limx14x13ex\lim_{x \to \infty} \frac{14x^{13}}{e^x}

Step 3: Repeat L'Hôpital's Rule

We are still at the indeterminate form \frac{\infty}{\infty}, so we apply L'Hôpital's Rule again:

  • Derivative of the numerator 14x1314x^{13} is 182x12182x^{12}.
  • Derivative of the denominator exe^x is still exe^x.

This results in:

limx182x12ex\lim_{x \to \infty} \frac{182x^{12}}{e^x}

Step 4: Continue differentiating

If we continue applying L'Hôpital's Rule repeatedly, each time we reduce the power of xx in the numerator by 1, while the denominator remains exe^x. After applying L'Hôpital's Rule 14 times, we will end up with:

limx14!ex\lim_{x \to \infty} \frac{14!}{e^x}

Since 14!14! is a constant and exe^x grows exponentially as xx \to \infty, the fraction approaches 0. Therefore:

limxx14ex=0\lim_{x \to \infty} \frac{x^{14}}{e^x} = 0

Final Answer:

The value of the limit is 0\boxed{0}.


Would you like more details about the solution or any related concepts? Here are some follow-up questions:

  1. How does the exponential function grow compared to polynomial functions as xx increases?
  2. What is the intuition behind why L'Hôpital's Rule works for indeterminate forms like \frac{\infty}{\infty}?
  3. What other types of indeterminate forms can L'Hôpital's Rule be applied to?
  4. How can we analyze limits of rational functions without L'Hôpital's Rule?
  5. What happens to limits of other types of functions as xx approaches infinity?

Tip: Remember that exponential functions like exe^x grow much faster than any polynomial, so in limits involving both, the polynomial will usually be dominated by the exponential term.

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Math Problem Analysis

Mathematical Concepts

Limits
Exponential Growth
L'Hôpital's Rule

Formulas

L'Hôpital's Rule: If lim f(x)/g(x) = indeterminate, then lim f'(x)/g'(x)
Derivative of x^n: nx^(n-1)
Derivative of e^x: e^x

Theorems

L'Hôpital's Rule

Suitable Grade Level

Grades 11-12