Limit of \( \displaystyle \frac{8 x^{2} - 6 x - 2}{2 x - 2} \) as \( x \to 1 \)
Problem 1.222 · medium
Evaluate \( \displaystyle \lim_{x \to 1} \frac{8 x^{2} - 6 x - 2}{2 x - 2} \).
- \[ \lim_{x \to 1^+}\left(\frac{8 x^{2} - 6 x - 2}{2 x - 2}\right) \]limit factorStart with the limit of the given function. Factor the numerator.✓ Proved
- \[ = \lim_{x \to 1^+}\left(\frac{\left(x - 1\right) \left(8 x + 2\right)}{2 x - 2}\right) \]factorFactor the quadratic expression further.✓ Proved
- \[ = \lim_{x \to 1^+}\left(4 x + 1\right) \]simplify cancelSimplify the constant factor 2/2. Cancel the common factor (x - 1).✓ Proved
- \[ = 5 \]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
| 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 2*x - 2 = 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 2*x - 2 = 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 undefined where 2*x - 2 = 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 6 | ✓ 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 — 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 2026-10-05qwen3.6:27b-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.