Derivative of \( \displaystyle 3 x \left(3 x^{2} - 3 x + 1\right) \)
Problem 2.98 · hard
Differentiate \( \displaystyle f(x) = 3 x \left(3 x^{2} - 3 x + 1\right) \).
- \[ \frac{d}{d x} 3 x \left(3 x^{2} - 3 x + 1\right) \]Start with the derivative of the function.✓ Proved
- \[ = 3 x \frac{d}{d x} \left(3 x^{2} - 3 x + 1\right) + \left(3 x^{2} - 3 x + 1\right) \frac{d}{d x} 3 x \]productApply the product rule.✓ Proved
- \[ = 9 x^{2} + 3 x \frac{d}{d x} \left(3 x^{2} - 3 x + 1\right) - 9 x + 3 \]constant-multipleDifferentiate the first part of the product.✓ Proved
- \[ = 9 x^{2} + x \left(18 x - 9\right) - 9 x + 3 \]derivative algebraDifferentiate the second part of the product. Distribute the 3 in the first term.✓ Proved
- \[ = 27 x^{2} - 18 x + 3 \]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
| 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 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 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 |
| 7 | ✓ 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 differentiated f directly and got the stated answer |
Reviewers
gpt-oss:20b: passdeepseek-r1:70b: passqwen3.6:27b-mlx: pass
Every verdict on record (12)
qwen3.6:27b-mlx: pass 2026-09-20gpt-oss:20b: pass 2026-09-20qwen3.6:27b-mlx: pass 2026-09-20gpt-oss:20b: pass 2026-09-20qwen3.6:27b-mlx: pass 2026-09-19deepseek-r1:70b: pass 2026-09-19gpt-oss:20b: pass 2026-09-19qwen3.6:27b-mlx: pass 2026-09-19deepseek-r1:70b: pass 2026-09-19gpt-oss:20b: pass 2026-09-19gpt-oss:20b: pass 2026-09-17deepseek-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.