Limit of \( \displaystyle \frac{2 x - 1}{\left(x - 1\right)^{2} + 3} \) as \( x \to \infty \)
Problem 1.260 · medium
Evaluate \( \displaystyle \lim_{x \to \infty} \frac{2 x - 1}{\left(x - 1\right)^{2} + 3} \).
- \[ \lim_{x \to \infty}\left(\frac{2 x - 1}{\left(x - 1\right)^{2} + 3}\right) \]limitStart with the original limit expression.✓ Proved
- \[ = \lim_{x \to \infty}\left(\frac{2 x - 1}{x^{2} - 2 x + 4}\right) \]algebra simplifyExpand the denominator. Combine the constant terms in the denominator.✓ Proved
- \[ = \lim_{x \to \infty}\left(\frac{\frac{2}{x} - \frac{1}{x^{2}}}{1 - \frac{2}{x} + \frac{4}{x^{2}}}\right) \]rewriteDivide the numerator and denominator by the highest power of x, which is x**2.✓ Proved
- \[ = \lim_{x \to \infty}\left(\frac{2}{x} - \frac{1}{x^{2}}\right) \left(\lim_{x \to \infty}\left(1 - \frac{2}{x} + \frac{4}{x^{2}}\right)\right)^{-1} \]limit-lawApply the quotient rule for limits.✓ Proved
- \[ = 0 \]limit simplifyEvaluate the limit of each part as x approaches infinity. Final result.✓ Proved
Answer \( 0 \)
✓ 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 (x - 1)**2 + 3 = 0 undefined where x**2 - 2*x + 4 = 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x**2 - 2*x + 4 = 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x**2 - 2*x + 4 = 0 undefined where x = 0 undefined where 1 - 2/x + 4/x**2 = 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x = 0 undefined where 1 - 2/x + 4/x**2 = 0 undefined where Limit(1 - 2/x + 4/x**2, x, oo, dir='-') = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where x = 0 undefined where Limit(1 - 2/x + 4/x**2, x, oo, dir='-') = 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
Every verdict on record (4)
qwen3.6:27b-mlx: pass 2026-10-05gpt-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.