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Derivative of \( \displaystyle 15 x \left(3 x^{2} + 3 x + 1\right) \)

Problem 2.984 · hard

Differentiate \( \displaystyle f(x) = 15 x \left(3 x^{2} + 3 x + 1\right) \).
  1. \[ \frac{d}{d x} 15 x \left(3 x^{2} + 3 x + 1\right) \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = \frac{d}{d x} \left(45 x^{3} + 45 x^{2} + 15 x\right) \]
    algebraDistribute 15*x into the parentheses.✓ Proved
  3. \[ = \frac{d}{d x} 15 x + \frac{d}{d x} 45 x^{2} + \frac{d}{d x} 45 x^{3} \]
    sumApply the sum rule for derivatives.✓ Proved
  4. \[ = 15 \frac{d}{d x} x + 45 \frac{d}{d x} x^{2} + 45 \frac{d}{d x} x^{3} \]
    constant-multipleFactor out the constants.✓ Proved
  5. \[ = 135 x^{2} + 90 x + 15 \]
    power algebraApply the power rule to each term. Multiply the coefficients.✓ Proved
Answer \( 15 \left(3 x + 1\right)^{2} \)

✓ 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
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
  • qwen3.6:27b-mlx: pass
Every verdict on record (4)
  • qwen3.6:27b-mlx: pass 2026-09-27
  • gpt-oss:20b: pass 2026-09-27
  • qwen3.6:27b-mlx: pass 2026-09-27 — The solution correctly expands the polynomial, applies linearity and the power rule, and simplifies the result. The final expression is algebraically equivalent to the stated answer.
  • gpt-oss:20b: pass 2026-09-27

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 2026-09-27 with SymPy 1.14.0.