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

Problem 2.68 · easy

Differentiate \( \displaystyle f(x) = x \left(3 x + 2\right) \).
  1. \[ \frac{d}{d x} x \left(3 x + 2\right) \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = \frac{d}{d x} \left(3 x^{2} + 2 x\right) \]
    algebra algebraDistribute x into the parentheses. Simplify the terms.✓ Proved
  3. \[ = \frac{d}{d x} 2 x + \frac{d}{d x} 3 x^{2} \]
    sumApply the sum rule.✓ Proved
  4. \[ = 2 \frac{d}{d x} x + 3 \frac{d}{d x} x^{2} \]
    constant-multiplePull out the constants.✓ Proved
  5. \[ = 6 x + 2 \]
    power algebraApply the power rule to each term. Multiply the terms.✓ Proved
Answer \( 6 x + 2 \)

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. The reviewers disagree about how one step is explained; every verdict is in the receipt.

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: pass
  • deepseek-r1:70b: pass
  • qwen3.6:27b-mlx: pass — The solution correctly applies the one-change-per-step rule, using valid labels from the fixed vocabulary for each transformation.
Every verdict on record (12)
  • qwen3.6:27b-mlx: pass 2026-09-20 — The solution correctly applies the one-change-per-step rule, using valid labels from the fixed vocabulary for each transformation.
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-20
  • gpt-oss:20b: fail (error) 2026-09-20 — Step 6 applies two different differentiation rules (power rule for 3*x**2 and the basic derivative of x for 2*x) but labels only "power". The derivative of x should be handled with the "derivative" rule, not "power".
  • 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
  • gpt-oss:20b: pass 2026-09-17
  • 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.