∫Calc Practice

Derivative of \( \displaystyle x \left(\ln{\left(4 x \right)} - 1\right) \)

Problem 2.376 · medium

Differentiate \( \displaystyle f(x) = x \left(\ln{\left(4 x \right)} - 1\right) \).
  1. \[ \frac{d}{d x} x \left(\ln{\left(4 x \right)} - 1\right) \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = x \frac{d}{d x} \left(\ln{\left(4 x \right)} - 1\right) + \left(\ln{\left(4 x \right)} - 1\right) \frac{d}{d x} x \]
    productApply the product rule.✓ Proved
  3. \[ = x \frac{d}{d x} \left(\ln{\left(4 x \right)} - 1\right) + \ln{\left(4 x \right)} - 1 \]
    derivativeDifferentiate the first part of the product.✓ Proved
  4. \[ = - x \frac{d}{d x} 1 + x \frac{d}{d x} \ln{\left(4 x \right)} + \ln{\left(4 x \right)} - 1 \]
    sumDistribute the derivative across the subtraction.✓ Proved
  5. \[ = x \frac{d}{d x} \ln{\left(4 x \right)} + \ln{\left(4 x \right)} - 1 \]
    derivative algebraDifferentiate the constant term. Simplify the zero term.✓ Proved
  6. \[ = \ln{\left(4 x \right)} \]
    chain algebra algebra simplifyApply the chain rule to the logarithm. Simplify the fraction by canceling the 4. Simplify the product of 1/x and x. Combine the remaining terms.✓ Proved
Answer \( \log{\left(4 x \right)} \)

✓ 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
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

  • gpt-oss:20b: pass
  • qwen3.6:27b-mlx: pass — The solution correctly applies the product rule, linearity of differentiation, and the chain rule for the logarithmic term. Each step isolates a single logical transformation, and the labels accurately reflect the operations performed.
Every verdict on record (6)
  • qwen3.6:27b-mlx: pass 2026-09-21 — The solution correctly applies the product rule, linearity of differentiation, and the chain rule for the logarithmic term. Each step isolates a single logical transformation, and the labels accurately reflect the operations performed.
  • gpt-oss:20b: pass 2026-09-21
  • qwen3.6:27b-mlx: pass 2026-09-20 — The solution correctly applies the product rule, linearity of differentiation, and the chain rule for the logarithmic term. Each step isolates a single operation and uses labels from the allowed vocabulary.
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-20 — The solution correctly applies the product rule, linearity of the derivative, and the chain rule for the logarithm. Each step isolates a single transformation, and the labels accurately reflect the operations performed.
  • 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.