∫Calc Practice

Derivative of \( \displaystyle 5 x \left(\ln{\left(3 x \right)} - 1\right) \)

Problem 2.703 · medium

Differentiate \( \displaystyle f(x) = 5 x \left(\ln{\left(3 x \right)} - 1\right) \).
  1. \[ \frac{d}{d x} 5 x \left(\ln{\left(3 x \right)} - 1\right) \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = 5 \frac{d}{d x} x \left(\ln{\left(3 x \right)} - 1\right) \]
    constant-multiplePull out the constant factor 5.✓ Proved
  3. \[ = 5 x \frac{d}{d x} \left(\ln{\left(3 x \right)} - 1\right) + 5 \left(\ln{\left(3 x \right)} - 1\right) \frac{d}{d x} x \]
    productApply the product rule.✓ Proved
  4. \[ = 5 x \frac{d}{d x} \left(\ln{\left(3 x \right)} - 1\right) + 5 \ln{\left(3 x \right)} - 5 \]
    derivative derivativeDifferentiate the first part of the product. Differentiate the first part of the second term.✓ Proved
  5. \[ = 5 x \left(- \frac{d}{d x} 1 + \frac{d}{d x} \ln{\left(3 x \right)}\right) + 5 \ln{\left(3 x \right)} - 5 \]
    sumSplit the derivative of the difference.✓ Proved
  6. \[ = 5 x \frac{d}{d x} \ln{\left(3 x \right)} + 5 \ln{\left(3 x \right)} - 5 \]
    derivativeThe derivative of the constant 1 is 0.✓ Proved
  7. \[ = 5 \ln{\left(3 x \right)} + \frac{5 \frac{d}{d x} 3 x}{3} - 5 \]
    chainApply the chain rule to the logarithm.✓ Proved
  8. \[ = 5 \ln{\left(3 x \right)} \]
    derivative algebra algebra simplifyDifferentiate the inner function 3*x. Simplify the fraction. Simplify the product of x and 1/x. Combine the terms to get the final answer.✓ Proved
Answer \( 5 \log{\left(3 x \right)} \)

✓ 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

  • gpt-oss:20b: pass
  • qwen3.6:27b-mlx: pass — The solution correctly applies differentiation rules step-by-step, adhering to the single-change constraint and using valid labels from the fixed vocabulary.
Every verdict on record (4)
  • qwen3.6:27b-mlx: pass 2026-09-21 — The solution correctly applies differentiation rules step-by-step, adhering to the single-change constraint and using valid labels from the fixed vocabulary.
  • gpt-oss:20b: pass 2026-09-21
  • qwen3.6:27b-mlx: pass 2026-09-21 — The solution correctly applies differentiation rules step-by-step, adhering to the one-change-per-step constraint. The labels used are appropriate for the operations performed.
  • gpt-oss:20b: fail (style) 2026-09-21 — Step 5 incorrectly labels an algebraic simplification as a derivative. The step merely removes the redundant multiplication by 1, which should be tagged as "algebra" (or "simplify"), not "derivative".

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.