Math Problem Statement

lim (x→∞) (2 - 3x + x^3) / (5x^2 - 7x + 1)

Solution

The given problem is:

limx23x+x35x27x+1.\lim_{x \to \infty} \frac{2 - 3x + x^3}{5x^2 - 7x + 1}.

Solution:

To find the limit as xx \to \infty, we analyze the degrees of the numerator and denominator.

  1. The numerator is 23x+x32 - 3x + x^3. The highest degree term is x3x^3.
  2. The denominator is 5x27x+15x^2 - 7x + 1. The highest degree term is 5x25x^2.

Observing growth:

As xx \to \infty, the x3x^3 term in the numerator grows much faster than the x2x^2 term in the denominator.

Dividing by the highest power of xx in the denominator:

Divide each term in both the numerator and denominator by x2x^2 (the highest degree term in the denominator):

limx23x+x35x27x+1=limx2x23x+x57x+1x2.\lim_{x \to \infty} \frac{2 - 3x + x^3}{5x^2 - 7x + 1} = \lim_{x \to \infty} \frac{\frac{2}{x^2} - \frac{3}{x} + x}{5 - \frac{7}{x} + \frac{1}{x^2}}.

Simplify:

  1. As xx \to \infty, 2x20\frac{2}{x^2} \to 0, 3x0\frac{3}{x} \to 0, and 1x20\frac{1}{x^2} \to 0.
  2. This leaves: limxx5.\lim_{x \to \infty} \frac{x}{5}.

Final result:

x5.\frac{x}{5} \to \infty.

So, the limit does not exist as it approaches infinity.

Would you like me to explore related examples or provide further clarification? Here are 5 related questions for practice:

  1. What is the limit of limxx2+2x5x2+1?\lim_{x \to \infty} \frac{x^2 + 2x}{5x^2 + 1}?
  2. How do you determine if a rational function's limit approaches zero?
  3. Can the degrees of numerator and denominator determine the behavior of the limit?
  4. How does dividing by the highest power of xx simplify such problems?
  5. Why does limx1x\lim_{x \to \infty} \frac{1}{x} always approach zero?

Tip: Always compare the growth rates of the highest degree terms in the numerator and denominator for rational functions.

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Math Problem Analysis

Mathematical Concepts

Limits
Asymptotic Behavior
Rational Functions

Formulas

lim (x→∞) f(x) = leading term of numerator / leading term of denominator
Behavior of terms as x approaches infinity (e.g., 1/x → 0)

Theorems

Degree Comparison of Polynomial Functions
Limit Laws for Polynomial and Rational Functions

Suitable Grade Level

Grades 11-12 or early college