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Derivative of \( \displaystyle 2 x \left(3 x + 2\right) \)

Problem 2.123 · easy

Differentiate \( \displaystyle f(x) = 2 x \left(3 x + 2\right) \).
  1. \[ \frac{d}{d x} 2 x \left(3 x + 2\right) \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = 2 x \frac{d}{d x} \left(3 x + 2\right) + \left(3 x + 2\right) \frac{d}{d x} 2 x \]
    productApply the product rule.✓ Proved
  3. \[ = 2 x \frac{d}{d x} \left(3 x + 2\right) + 6 x + 4 \]
    constant-multipleFactor out the constant 2 from the first term.✓ Proved
  4. \[ = 2 x \left(\frac{d}{d x} 2 + \frac{d}{d x} 3 x\right) + 6 x + 4 \]
    sumApply the sum rule to the second term.✓ Proved
  5. \[ = 2 x \left(\frac{d}{d x} 2 + 3\right) + 6 x + 4 \]
    derivativeDifferentiate 3*x.✓ Proved
  6. \[ = 12 x + 4 \]
    derivative algebra algebra algebraDifferentiate the constant 2. Simplify the expression. Distribute the 2. Combine like terms.✓ Proved
Answer \( 12 x + 4 \)

✓ 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
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
9✓ 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: pass
  • deepseek-r1:70b: pass
  • qwen3.6:27b-mlx: pass
Every verdict on record (15)
  • qwen3.6:27b-mlx: pass 2026-09-20
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-20
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-19
  • deepseek-r1:70b: pass 2026-09-19
  • gpt-oss:20b: pass 2026-09-19
  • qwen3.6:27b-mlx: pass 2026-09-19
  • deepseek-r1:70b: pass 2026-09-19
  • gpt-oss:20b: pass 2026-09-19
  • qwen3.6:27b-mlx: pass 2026-09-18
  • deepseek-r1:70b: pass 2026-09-18
  • gpt-oss:20b: pass 2026-09-18
  • gpt-oss:20b: fail 2026-09-17 — Step 3 mislabels the operation as a constant‑multiple rule and the note claims to factor out a constant, but it actually evaluates the derivative of 2*x. The rule label and explanatory note do not match the action performed.
  • deepseek-r1:70b: pass 2026-09-17

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 2026-09-26 with SymPy 1.14.0.