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Derivative of \( \displaystyle 3 x \left(3 x^{2} - 3 x + 1\right) \)

Problem 2.98 · hard

Differentiate \( \displaystyle f(x) = 3 x \left(3 x^{2} - 3 x + 1\right) \).
  1. \[ \frac{d}{d x} 3 x \left(3 x^{2} - 3 x + 1\right) \]
    Start with the derivative of the function.✓ Proved
  2. \[ = 3 x \frac{d}{d x} \left(3 x^{2} - 3 x + 1\right) + \left(3 x^{2} - 3 x + 1\right) \frac{d}{d x} 3 x \]
    productApply the product rule.✓ Proved
  3. \[ = 9 x^{2} + 3 x \frac{d}{d x} \left(3 x^{2} - 3 x + 1\right) - 9 x + 3 \]
    constant-multipleDifferentiate the first part of the product.✓ Proved
  4. \[ = 9 x^{2} + x \left(18 x - 9\right) - 9 x + 3 \]
    derivative algebraDifferentiate the second part of the product. Distribute the 3 in the first term.✓ Proved
  5. \[ = 27 x^{2} - 18 x + 3 \]
    algebra simplifyDistribute the 3*x in the second term. Combine like terms.✓ Proved
Answer \( 3 \left(3 x - 1\right)^{2} \)

✓ 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: pass
  • deepseek-r1:70b: pass
  • qwen3.6:27b-mlx: pass
Every verdict on record (12)
  • 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
  • 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.