∫Calc Practice
Home›Calculus 1›Power rule›Problem 2.1130

Derivative of \( \displaystyle x \left(- 4 x^{2} - 6 x - 3\right) \)

Problem 2.1130 · hard

Differentiate \( \displaystyle f(x) = x \left(- 4 x^{2} - 6 x - 3\right) \).
  1. \[ \frac{d}{d x} x \left(- 4 x^{2} - 6 x - 3\right) \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = x \frac{d}{d x} \left(- 4 x^{2} - 6 x - 3\right) + \left(- 4 x^{2} - 6 x - 3\right) \frac{d}{d x} x \]
    productApply the product rule.✓ Proved
  3. \[ = - 4 x^{2} + x \frac{d}{d x} \left(- 4 x^{2} - 6 x - 3\right) - 6 x - 3 \]
    derivative constant-multipleDifferentiate the first part of the product. Simplify the first term.✓ Proved
  4. \[ = - 4 x^{2} + x \left(- 8 x - 6\right) - 6 x - 3 \]
    derivativeDifferentiate the second part of the product.✓ Proved
  5. \[ = - 12 x^{2} - 12 x - 3 \]
    algebra simplifyDistribute x into the parentheses. Combine like terms.✓ Proved
Answer \( - 3 \left(2 x + 1\right)^{2} \)

✓ 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
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 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 differentiated f directly and got the stated answer

Reviewers

  • gpt-oss:20b: fail (style) — Step 4 applies an algebraic simplification (removing the leading 1) but is labeled "constant-multiple"; the correct label would be "algebra".
  • qwen3.6:27b-mlx: pass
Every verdict on record (4)
  • qwen3.6:27b-mlx: pass 2026-09-28
  • gpt-oss:20b: fail (style) 2026-09-28 — Step 4 applies an algebraic simplification (removing the leading 1) but is labeled "constant-multiple"; the correct label would be "algebra".
  • qwen3.6:27b-mlx: pass 2026-09-28
  • gpt-oss:20b: fail (style) 2026-09-28 — Step 4 incorrectly labels the simplification of 1*(-4*x**2 - 6*x - 3) as "constant-multiple"; it should be "algebra".

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 2026-09-28 with SymPy 1.14.0.