Derivative of \( \displaystyle 4 x \left(4 x^{2} + 6 x + 3\right) \)
Problem 2.391 · hard
Differentiate \( \displaystyle f(x) = 4 x \left(4 x^{2} + 6 x + 3\right) \).
- \[ \frac{d}{d x} 4 x \left(4 x^{2} + 6 x + 3\right) \]Start with the derivative of the function.✓ Proved
- \[ = \frac{d}{d x} \left(16 x^{3} + 24 x^{2} + 12 x\right) \]algebraDistribute 4*x into the parentheses.✓ Proved
- \[ = \frac{d}{d x} 12 x + \frac{d}{d x} 24 x^{2} + \frac{d}{d x} 16 x^{3} \]sumApply the sum rule for derivatives.✓ Proved
- \[ = 12 \frac{d}{d x} x + 24 \frac{d}{d x} x^{2} + 16 \frac{d}{d x} x^{3} \]constant-multipleFactor out the constants.✓ Proved
- \[ = 48 x^{2} + 48 x + 12 \]power simplifyApply the power rule to each term. Multiply the constants to get the final result.✓ Proved
Answer \( 12 \left(2 x + 1\right)^{2} \)
✓ 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
| 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 |
| 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: passqwen3.6:27b-mlx: pass
Every verdict on record (6)
qwen3.6:27b-mlx: pass 2026-09-21gpt-oss:20b: pass 2026-09-21qwen3.6:27b-mlx: pass 2026-09-20 — The solution correctly applies the rules in a single-change-per-step manner. The algebraic expansion, sum rule, constant multiple rule, and power rule are all labeled correctly and applied sequentially.gpt-oss:20b: fail (style) 2026-09-20 — Step 1 is unlabeled; it should explicitly state the rule used (e.g., “rewrite” for expanding the product) to satisfy the requirement that each step names a rule from the allowed vocabulary.qwen3.6:27b-mlx: pass 2026-09-20 — The solution correctly expands the function, applies the sum and constant-multiple rules, and uses the power rule. The final result matches the stated answer.gpt-oss:20b: pass 2026-09-20
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.