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Limit of \( \displaystyle \frac{\sqrt{4 x^{2} + 1}}{2 x} \) as \( x \to \infty \)

Problem 1.147 · medium

Evaluate \( \displaystyle \lim_{x \to \infty} \frac{\sqrt{4 x^{2} + 1}}{2 x} \).
  1. \[ \lim_{x \to \infty}\left(\frac{\sqrt{4 x^{2} + 1}}{2 x}\right) \]
    limitIdentify the limit to evaluate.✓ Proved
  2. \[ = \lim_{x \to \infty}\left(\frac{\sqrt{4 + \frac{1}{x^{2}}} \left|{x}\right|}{2 x}\right) \]
    factor algebra simplifyFactor out x**2 from the radicand. Apply the property sqrt(a*b) = sqrt(a)*sqrt(b). Simplify the square root of x**2.✓ Proved
  3. \[ = \lim_{x \to \infty}\left(\frac{\sqrt{4 + \frac{1}{x^{2}}}}{2}\right) \]
    simplify cancelSince x approaches infinity, |x| = x. Cancel the common factor of x in the numerator and denominator.✓ Proved
  4. \[ = \frac{\lim_{x \to \infty} 2}{2} \]
    limit-lawApply the limit law for a quotient.✓ Proved
  5. \[ = 1 \]
    simplify simplifyEvaluate the limit of the constant term. Final simplification.✓ Proved
Answer \( 1 \)

✓ Nihil obstat Every line of this solution was proved by the computer algebra system SymPy. The answer was also checked a second way, without looking at the solution. Reviewers found nothing wrong with the explanation.

The full receipt
LineStatusChecked byDetail
1✓ Provedsympy 1.14.0line 1 is the problem as stated
2✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x = 0
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x = 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x = 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x = 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x = 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x = 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
9✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
answer, a second way✓ Provedsympy 1.14.0SymPy took the limit from both sides and got the stated value

Reviewers

  • gpt-oss:20b: pass
  • qwen3.6:27b-mlx: pass — The solution correctly factors, simplifies the square root using the domain constraint, cancels terms, and applies limit laws. Each step changes only one aspect of the expression and uses valid labels from the vocabulary.
Every verdict on record (4)
  • qwen3.6:27b-mlx: pass 2026-10-04 — The solution correctly factors, simplifies the square root using the domain constraint, cancels terms, and applies limit laws. Each step changes only one aspect of the expression and uses valid labels from the vocabulary.
  • gpt-oss:20b: pass 2026-10-04
  • qwen3.6:27b-mlx: pass 2026-10-04
  • gpt-oss:20b: pass 2026-10-04

Proved: SymPy reduced the difference between the two sides to zero. Checked independently: a separate method, named above, confirmed it. Checked numerically: the two sides agree at every sampled point, which is evidence, not proof. Reviewed: a model or a person read it; that is all a sentence can have. Solution by gemma4:26b, checked 2026-10-04 with SymPy 1.14.0.