Math Problem Statement

lim x→+∞

(e^

1−x)/

(1/x)

Solution

We are asked to compute the limit:

limx+e1x1/x\lim_{x \to +\infty} \frac{e^{1-x}}{1/x}

Step-by-step Solution:

  1. Rewrite the expression:

    We can rewrite the limit as:

    limx+e1x1/x=limx+e1xx\lim_{x \to +\infty} \frac{e^{1-x}}{1/x} = \lim_{x \to +\infty} e^{1-x} \cdot x

  2. Simplify the exponent:

    The expression e1xe^{1-x} can be rewritten as:

    e1x=eexe^{1-x} = e \cdot e^{-x}

    Thus, the limit becomes:

    limx+xeex\lim_{x \to +\infty} x \cdot e \cdot e^{-x}

    or simply:

    elimx+xexe \lim_{x \to +\infty} x e^{-x}

  3. Evaluate the limit:

    To compute limx+xex\lim_{x \to +\infty} x e^{-x}, notice that exe^{-x} decays exponentially, while xx grows linearly. Exponentially decaying functions approach zero much faster than linear growth, so this product tends to 0:

    limx+xex=0\lim_{x \to +\infty} x e^{-x} = 0

  4. Final Answer:

    Therefore, multiplying by ee, we get:

    limx+e1xx=e0=0\lim_{x \to +\infty} e^{1-x} \cdot x = e \cdot 0 = 0

Conclusion:

limx+e1x1/x=0\lim_{x \to +\infty} \frac{e^{1-x}}{1/x} = 0

Would you like more details or have any questions?

Here are 5 related questions for further exploration:

  1. What is the limit of limx+x2ex\lim_{x \to +\infty} \frac{x^2}{e^x}?
  2. How do we apply L'Hopital's Rule to indeterminate forms in limits?
  3. How does the behavior of exe^x compare to polynomial functions as x+x \to +\infty?
  4. Can you explain the comparison between exponential growth and linear growth in limits?
  5. How can we approximate limits involving exponential and logarithmic functions?

Tip: Exponentially decaying functions like exe^{-x} tend to dominate polynomial terms as x+x \to +\infty, leading the whole expression to approach zero.

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Math Problem Analysis

Mathematical Concepts

Calculus
Limits
Exponential Functions

Formulas

lim_{x \to +\infty} \frac{e^{1-x}}{1/x} = e \lim_{x \to +\infty} x e^{-x}
Exponential decay: e^{-x}

Theorems

Limit of exponential decay vs. polynomial growth

Suitable Grade Level

Undergraduate Calculus (Grades 11-12 and above)