∫Calc Practice

Limit of \( \displaystyle \frac{- 3 x + 2 \left(x + 1\right)^{2} - 5}{x - 1} \) as \( x \to 1 \)

Problem 1.96 · medium

Evaluate \( \displaystyle \lim_{x \to 1} \frac{- 3 x + 2 \left(x + 1\right)^{2} - 5}{x - 1} \).
  1. \[ \lim_{x \to 1^+}\left(\frac{- 3 x + 2 \left(x + 1\right)^{2} - 5}{x - 1}\right) \]
    limitStart with the limit of the given function.✓ Proved
  2. \[ = \lim_{x \to 1^+}\left(\frac{2 x^{2} + x - 3}{x - 1}\right) \]
    algebra algebra simplify rewriteExpand the squared term. Distribute the 2. Combine like terms in the numerator. Rewrite the numerator to reveal a factor of (x-1).✓ Proved
  3. \[ = \lim_{x \to 1^+}\left(\frac{2 x \left(x - 1\right) + 3 x - 3}{x - 1}\right) \]
    factorFactor out (x - 1) from the numerator.✓ Proved
  4. \[ = \lim_{x \to 1^+}\left(2 x + 3\right) \]
    simplifyCancel the common factor (x - 1).✓ Proved
  5. \[ = 5 \]
    limitEvaluate the limit by substituting x = 1.✓ Proved
Answer \( 5 \)

✓ 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 = 0
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x - 1 = 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x - 1 = 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x - 1 = 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x - 1 = 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where x - 1 = 0
8✓ 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 applies algebraic manipulation to resolve the indeterminate form, with each step changing only one aspect of the expression and using appropriate labels from the fixed vocabulary.
Every verdict on record (4)
  • qwen3.6:27b-mlx: pass 2026-10-03 — The solution correctly applies algebraic manipulation to resolve the indeterminate form, with each step changing only one aspect of the expression and using appropriate labels from the fixed vocabulary.
  • gpt-oss:20b: pass 2026-10-03
  • qwen3.6:27b-mlx: pass 2026-09-30
  • gpt-oss:20b: pass 2026-09-30

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.