∫Calc Practice

Derivative of \( \displaystyle \frac{\ln{\left(2 x \right)}}{4 x^{2}} \)

Problem 2.456 · hard

Differentiate \( \displaystyle f(x) = \frac{\ln{\left(2 x \right)}}{4 x^{2}} \).
  1. \[ \frac{d}{d x} \frac{\ln{\left(2 x \right)}}{4 x^{2}} \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = \frac{\frac{d}{d x} \ln{\left(2 x \right)}}{4 x^{2}} - \frac{\ln{\left(2 x \right)} \frac{d}{d x} 4 x^{2}}{16 x^{4}} \]
    quotientApply the quotient rule.✓ Proved
  3. \[ = - \frac{\ln{\left(2 x \right)}}{2 x^{3}} + \frac{1}{4 x^{3}} \]
    chain algebra algebra algebraDifferentiate the numerator using the chain rule. Simplify the numerator of the first term. Simplify the first term. Simplify the second term.✓ Proved
  4. \[ = \frac{1 - 2 \ln{\left(2 x \right)}}{4 x^{3}} \]
    algebraCombine the terms over a common denominator.✓ Proved
  5. \[ = \frac{- 2 \ln{\left(x \right)} - 2 \ln{\left(2 \right)} + 1}{4 x^{3}} \]
    algebra algebraExpand the logarithm. Distribute the constant.✓ Proved
  6. \[ = \frac{1 - 2 \ln{\left(2 x \right)}}{4 x^{3}} \]
    simplifyFinal simplified form.✓ Proved
Answer \( \frac{1 - 2 \log{\left(2 x \right)}}{4 x^{3}} \)

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. The reviewers disagree about how one step is explained; every verdict is in the receipt.

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
undefined where x = 0
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where x = 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where x = 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where x = 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where x = 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where x = 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where x = 0
9✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where x = 0
10✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where x = 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
log is undefined for non-positive arguments
undefined where x = 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 — The solution correctly applies the quotient rule and chain rule, followed by valid algebraic simplifications. The final steps expanding and recombining the logarithm are redundant but mathematically correct and do not violate the single-rule-per-step constraint.
Every verdict on record (6)
  • qwen3.6:27b-mlx: pass 2026-09-21 — The solution correctly applies the quotient rule and chain rule, followed by valid algebraic simplifications. The final steps expanding and recombining the logarithm are redundant but mathematically correct and do not violate the single-rule-per-step constraint.
  • gpt-oss:20b: pass 2026-09-21
  • qwen3.6:27b-mlx: fail (error) 2026-09-20 — Step 3 is labeled 'chain' but performs two distinct operations: differentiating the numerator (chain rule) and the denominator (power rule). The contract requires each step to change only one thing.
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-20 — The solution correctly applies the quotient rule, chain rule, and algebraic simplifications. Each step changes only one aspect of the expression, and the labels accurately reflect the rules applied.
  • 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.