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Home›Calculus 1›Limits at infinity›Problem 1.260

Limit of \( \displaystyle \frac{2 x - 1}{\left(x - 1\right)^{2} + 3} \) as \( x \to \infty \)

Problem 1.260 · medium

Evaluate \( \displaystyle \lim_{x \to \infty} \frac{2 x - 1}{\left(x - 1\right)^{2} + 3} \).
  1. \[ \lim_{x \to \infty}\left(\frac{2 x - 1}{\left(x - 1\right)^{2} + 3}\right) \]
    limitStart with the original limit expression.✓ Proved
  2. \[ = \lim_{x \to \infty}\left(\frac{2 x - 1}{x^{2} - 2 x + 4}\right) \]
    algebra simplifyExpand the denominator. Combine the constant terms in the denominator.✓ Proved
  3. \[ = \lim_{x \to \infty}\left(\frac{\frac{2}{x} - \frac{1}{x^{2}}}{1 - \frac{2}{x} + \frac{4}{x^{2}}}\right) \]
    rewriteDivide the numerator and denominator by the highest power of x, which is x**2.✓ Proved
  4. \[ = \lim_{x \to \infty}\left(\frac{2}{x} - \frac{1}{x^{2}}\right) \left(\lim_{x \to \infty}\left(1 - \frac{2}{x} + \frac{4}{x^{2}}\right)\right)^{-1} \]
    limit-lawApply the quotient rule for limits.✓ Proved
  5. \[ = 0 \]
    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
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 - 1)**2 + 3 = 0
undefined where x**2 - 2*x + 4 = 0
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x**2 - 2*x + 4 = 0
4✓ Provedsympy 1.14.0simplify(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✓ Provedsympy 1.14.0simplify(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✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x = 0
undefined where Limit(1 - 2/x + 4/x**2, x, oo, dir='-') = 0
7✓ 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
Every verdict on record (4)
  • qwen3.6:27b-mlx: pass 2026-10-05
  • gpt-oss:20b: pass 2026-10-05
  • qwen3.6:27b-mlx: pass 2026-10-05
  • gpt-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.