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Derivative of \( \displaystyle x^{2} \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) \)

Problem 2.13 · hard

Differentiate \( \displaystyle f(x) = x^{2} \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) \).
  1. \[ \frac{d}{d x} x^{2} \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = x^{2} \frac{d}{d x} \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) + \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) \frac{d}{d x} x^{2} \]
    productApply the product rule.✓ Proved
  3. \[ = x^{2} \frac{d}{d x} \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) + 2 x \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) \]
    derivativeDifferentiate the first part of the product.✓ Proved
  4. \[ = x^{2} \left(- \frac{d}{d x} \frac{1}{2} + \frac{d}{d x} \ln{\left(2 x \right)}\right) + 2 x \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) \]
    sumDistribute the derivative to the terms in the parentheses.✓ Proved
  5. \[ = x^{2} \frac{d}{d x} \ln{\left(2 x \right)} + 2 x \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) \]
    constant algebraThe derivative of the constant 1/2 is 0. Simplify the expression by removing the zero term.✓ Proved
  6. \[ = 2 x \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) + \frac{x \frac{d}{d x} 2 x}{2} \]
    chainApply the chain rule to the logarithm.✓ Proved
  7. \[ = 2 x \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) + x \]
    derivative algebra algebraDifferentiate the inner function 2*x. Simplify the product of 1/(2*x) and 2. Simplify the term x**2 * (1/x).✓ Proved
  8. \[ = 2 x \ln{\left(2 x \right)} \]
    algebra simplifyDistribute 2*x into the parentheses. Combine like terms.✓ Proved
Answer \( 2 x \log{\left(2 x \right)} \)

✓ 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
log is undefined for non-positive arguments
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
9✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
10✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
11✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
12✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
log is undefined for non-positive arguments
answer, a second way✓ Provedsympy 1.14.0SymPy differentiated f directly and got the stated answer

Reviewers

  • deepseek-r1:70b: pass
  • gpt-oss:20b: pass
  • qwen3.6:27b-mlx: pass — The solution correctly applies the product rule, chain rule, and algebraic simplifications in distinct steps. All labels are appropriate for the operations performed.
Every verdict on record (14)
  • qwen3.6:27b-mlx: pass 2026-09-20 — The solution correctly applies the product rule, chain rule, and algebraic simplifications in distinct steps. All labels are appropriate for the operations performed.
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-20 — The solution correctly applies the product rule, chain rule, and algebraic simplifications in distinct steps. All labels are appropriate for the operations performed.
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-19 — The solution correctly applies the product rule, chain rule, and algebraic simplifications in a step-by-step manner. Each step changes only one aspect of the expression and uses valid labels from the provided vocabulary.
  • deepseek-r1:70b: pass 2026-09-19
  • gpt-oss:20b: pass 2026-09-19
  • qwen3.6:27b-mlx: pass 2026-09-19 — The solution correctly applies the product rule, chain rule, and algebraic simplifications in distinct steps. All labels are appropriate and the logic is sound.
  • deepseek-r1:70b: pass 2026-09-19
  • gpt-oss:20b: pass 2026-09-19
  • qwen3.6:27b-mlx: pass 2026-09-18 — The solution correctly applies the product rule, chain rule, and algebraic simplifications in distinct steps. All labels are appropriate and consistent with the provided vocabulary.
  • deepseek-r1:70b: pass 2026-09-18
  • gpt-oss:20b: pass 2026-09-18
  • deepseek-r1:70b: pass 2026-09-16

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.