Limit of \( \displaystyle \frac{\sqrt{\left(3 x - 1\right)^{2} + 1}}{3 x - 1} \) as \( x \to \infty \)
Problem 1.244 · medium
Evaluate \( \displaystyle \lim_{x \to \infty} \frac{\sqrt{\left(3 x - 1\right)^{2} + 1}}{3 x - 1} \).
- \[ \lim_{x \to \infty}\left(\frac{\sqrt{\left(3 x - 1\right)^{2} + 1}}{3 x - 1}\right) \]limitEvaluate the limit as x approaches infinity.✓ Proved
- \[ = \lim_{x \to \infty}\left(\frac{\sqrt{1 + \frac{1}{\left(3 x - 1\right)^{2}}} \left|{3 x - 1}\right|}{3 x - 1}\right) \]algebra algebra simplifyFactor out (3*x - 1)**2 from the radicand. Use the property sqrt(a*b) = sqrt(a)*sqrt(b). Simplify the square root of the squared term.✓ Proved
- \[ = \lim_{x \to \infty} \sqrt{1 + \frac{1}{\left(3 x - 1\right)^{2}}} \]simplifySince x approaches infinity, 3*x - 1 is positive, so abs(3*x - 1)/(3*x - 1) = 1.✓ Proved
- \[ = \lim_{x \to \infty} 1 \]limit-lawThe term 1/(3*x - 1)**2 approaches 0 as x approaches infinity.✓ Proved
- \[ = 1 \]limitEvaluate the final expression.✓ 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
| Line | Status | Checked by | Detail |
|---|---|---|---|
| 1 | ✓ Proved | sympy 1.14.0 | line 1 is the problem as stated |
| 2 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 3*x - 1 = 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 3*x - 1 = 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 3*x - 1 = 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 3*x - 1 = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 3*x - 1 = 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| answer | ✓ Proved | sympy 1.14.0 | final line against the stated answer: simplify(a - b) reduced to 0 |
| answer, a second way | ✓ Proved | sympy 1.14.0 | SymPy took the limit from both sides and got the stated value |
Reviewers
gpt-oss:20b: passqwen3.6:27b-mlx: pass — The solution correctly handles the absolute value arising from the square root of a squared term and applies limit laws appropriately. 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 2026-10-05 — The solution correctly handles the absolute value arising from the square root of a squared term and applies limit laws appropriately. Each step changes only one aspect of the expression and uses valid labels from the vocabulary.gpt-oss:20b: pass 2026-10-05qwen3.6:27b-mlx: pass 2026-10-05gpt-oss:20b: pass 2026-10-05
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 2026-10-05 with SymPy 1.14.0.