∫Calc Practice
Home›Calculus 1›Limits by factoring›Problem 1.111

Limit of \( \displaystyle \frac{- 5 x + \left(x - 1\right)^{2} + 11}{x - 4} \) as \( x \to 4 \)

Problem 1.111 · medium

Evaluate \( \displaystyle \lim_{x \to 4} \frac{- 5 x + \left(x - 1\right)^{2} + 11}{x - 4} \).
  1. \[ \lim_{x \to 4^+}\left(\frac{- 5 x + \left(x - 1\right)^{2} + 11}{x - 4}\right) \]
    limitState the original limit problem.✓ Proved
  2. \[ = \lim_{x \to 4^+}\left(\frac{x^{2} - 7 x + 12}{x - 4}\right) \]
    algebra simplifyExpand the squared term. Combine like terms in the numerator.✓ Proved
  3. \[ = \lim_{x \to 4^+}\left(x - 3\right) \]
    factor cancelFactor the quadratic numerator. Cancel the common factor (x - 4).✓ Proved
  4. \[ = 1 \]
    limitEvaluate the limit by substitution.✓ 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 - 4 = 0
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x - 4 = 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x - 4 = 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
6✓ 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 2026-10-03
  • gpt-oss:20b: pass 2026-10-03
  • qwen3.6:27b-mlx: pass 2026-10-03
  • gpt-oss:20b: pass 2026-10-03

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 2026-10-03 with SymPy 1.14.0.