Infinity Math Example 1

Follow the full solution, then compare it with the other examples linked below.

Example 1

easy
Evaluate limโกxโ†’โˆž3x2+5x2โˆ’1\lim_{x \to \infty} \frac{3x^2 + 5}{x^2 - 1}.

Solution

  1. 1
    Divide numerator and denominator by the highest power of xx in the denominator, x2x^2.
  2. 2
    Numerator: 3x2+5x2=3+5x2\frac{3x^2 + 5}{x^2} = 3 + \frac{5}{x^2}. Denominator: x2โˆ’1x2=1โˆ’1x2\frac{x^2-1}{x^2} = 1 - \frac{1}{x^2}.
  3. 3
    As xโ†’โˆžx \to \infty, 5x2โ†’0\frac{5}{x^2} \to 0 and 1x2โ†’0\frac{1}{x^2} \to 0.
  4. 4
    Limit: 3+01โˆ’0=3\frac{3 + 0}{1 - 0} = 3.

Answer

33
For rational functions at infinity, divide by the highest power of xx in the denominator. Terms with xx in the denominator vanish, leaving only the ratio of leading coefficients. When degrees are equal, the limit is the ratio of leading coefficients.

About Infinity

A concept representing a quantity that grows without bound โ€” infinity is not a real number but a description of unbounded behavior.

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