∫Calc Practice

Derivative of \( \displaystyle \frac{x^{2} \left(2 \ln{\left(x \right)} - 1\right)}{4} \)

Problem 2.215 · hard Beautiful

Differentiate \( \displaystyle f(x) = \frac{x^{2} \left(2 \ln{\left(x \right)} - 1\right)}{4} \).
  1. \[ \frac{d}{d x} \frac{x^{2} \left(2 \ln{\left(x \right)} - 1\right)}{4} \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = \frac{\frac{d}{d x} x^{2} \left(2 \ln{\left(x \right)} - 1\right)}{4} \]
    constant-multiplePull out the constant factor 1/4.✓ Proved
  3. \[ = \frac{x^{2} \frac{d}{d x} \left(2 \ln{\left(x \right)} - 1\right)}{4} + \frac{\left(2 \ln{\left(x \right)} - 1\right) \frac{d}{d x} x^{2}}{4} \]
    productApply the product rule.✓ Proved
  4. \[ = \frac{x^{2} \frac{d}{d x} \left(2 \ln{\left(x \right)} - 1\right)}{4} + \frac{x \left(2 \ln{\left(x \right)} - 1\right)}{2} \]
    derivativeDifferentiate x**2.✓ Proved
  5. \[ = \frac{x^{2} \left(- \frac{d}{d x} 1 + \frac{d}{d x} 2 \ln{\left(x \right)}\right)}{4} + \frac{x \left(2 \ln{\left(x \right)} - 1\right)}{2} \]
    sumDifferentiate the sum inside the parentheses.✓ Proved
  6. \[ = \frac{x^{2} \frac{d}{d x} \ln{\left(x \right)}}{2} + \frac{x \left(2 \ln{\left(x \right)} - 1\right)}{2} \]
    derivativeDifferentiate 2*log(x) and 1.✓ Proved
  7. \[ = \frac{x \left(2 \ln{\left(x \right)} - 1\right)}{2} + \frac{x}{2} \]
    derivative algebraDifferentiate log(x). Simplify the term x**2 * (2/x).✓ Proved
  8. \[ = x \ln{\left(x \right)} \]
    algebra algebra simplifyDistribute 2*x into the parentheses. Combine like terms. Final simplification.✓ Proved
Answer \( x \log{\left(x \right)} \)

✓ 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
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
  • deepseek-r1:70b: pass
  • qwen3.6:27b-mlx: pass
Every verdict on record (15)
  • qwen3.6:27b-mlx: pass 2026-09-20
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-20
  • gpt-oss:20b: pass 2026-09-20
  • qwen3.6:27b-mlx: pass 2026-09-19
  • deepseek-r1:70b: pass 2026-09-19
  • gpt-oss:20b: pass 2026-09-19
  • qwen3.6:27b-mlx: pass 2026-09-19
  • deepseek-r1:70b: fail (misleading) 2026-09-19 — Step 7 incorrectly labels an algebraic simplification as a derivative.
  • gpt-oss:20b: pass 2026-09-19
  • qwen3.6:27b-mlx: pass 2026-09-18 — The solution correctly applies differentiation rules step-by-step, adhering to the single-change constraint and using valid labels from the fixed vocabulary.
  • deepseek-r1:70b: fail (error) 2026-09-18 — Step 7 incorrectly labels an algebraic simplification as a derivative.
  • gpt-oss:20b: pass 2026-09-18
  • gpt-oss:20b: pass 2026-09-17
  • deepseek-r1:70b: pass 2026-09-17

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.