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Derivative of \( \displaystyle x \left(6 - 5 x\right) \)

Problem 2.1105 · medium

Differentiate \( \displaystyle f(x) = x \left(6 - 5 x\right) \).
  1. \[ \frac{d}{d x} x \left(6 - 5 x\right) \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = \frac{d}{d x} \left(- 5 x^{2} + 6 x\right) \]
    algebraDistribute x into the parentheses.✓ Proved
  3. \[ = \frac{d}{d x} 6 x - \frac{d}{d x} 5 x^{2} \]
    sumApply the difference rule.✓ Proved
  4. \[ = 6 \frac{d}{d x} x - 5 \frac{d}{d x} x^{2} \]
    constantPull out the constant factor.✓ Proved
  5. \[ = 6 - 5 \frac{d}{d x} x^{2} \]
    derivative simplifyDifferentiate the first term. Simplify the expression.✓ Proved
  6. \[ = 6 - 10 x \]
    power algebraApply the power rule to x**2. Multiply the constants.✓ Proved
Answer \( 6 - 10 x \)

✓ 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
8✓ 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 2026-09-28
  • gpt-oss:20b: pass 2026-09-28
  • qwen3.6:27b-mlx: pass 2026-09-28
  • gpt-oss:20b: pass 2026-09-28

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 2026-09-28 with SymPy 1.14.0.