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Home›Calculus 1›Limits by factoring›Problem 1.222

Limit of \( \displaystyle \frac{8 x^{2} - 6 x - 2}{2 x - 2} \) as \( x \to 1 \)

Problem 1.222 · medium

Evaluate \( \displaystyle \lim_{x \to 1} \frac{8 x^{2} - 6 x - 2}{2 x - 2} \).
  1. \[ \lim_{x \to 1^+}\left(\frac{8 x^{2} - 6 x - 2}{2 x - 2}\right) \]
    limit factorStart with the limit of the given function. Factor the numerator.✓ Proved
  2. \[ = \lim_{x \to 1^+}\left(\frac{\left(x - 1\right) \left(8 x + 2\right)}{2 x - 2}\right) \]
    factorFactor the quadratic expression further.✓ Proved
  3. \[ = \lim_{x \to 1^+}\left(4 x + 1\right) \]
    simplify cancelSimplify the constant factor 2/2. Cancel the common factor (x - 1).✓ Proved
  4. \[ = 5 \]
    limitEvaluate the limit by substitution.✓ 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 2*x - 2 = 0
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 2*x - 2 = 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
undefined where 2*x - 2 = 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 — The solution correctly factors the numerator, cancels common terms, and evaluates the limit. Each step applies a single rule and uses labels from the allowed vocabulary.
Every verdict on record (4)
  • qwen3.6:27b-mlx: pass 2026-10-05 — The solution correctly factors the numerator, cancels common terms, and evaluates the limit. Each step applies a single rule and uses labels from the allowed vocabulary.
  • 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.