Derivative of \( \displaystyle x^{2} \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) \)
Problem 2.13 · hard
Differentiate \( \displaystyle f(x) = x^{2} \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) \).
- \[ \frac{d}{d x} x^{2} \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) \]derivativeStart with the derivative of the function.✓ Proved
- \[ = x^{2} \frac{d}{d x} \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) + \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) \frac{d}{d x} x^{2} \]productApply the product rule.✓ Proved
- \[ = x^{2} \frac{d}{d x} \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) + 2 x \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) \]derivativeDifferentiate the first part of the product.✓ Proved
- \[ = x^{2} \left(- \frac{d}{d x} \frac{1}{2} + \frac{d}{d x} \ln{\left(2 x \right)}\right) + 2 x \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) \]sumDistribute the derivative to the terms in the parentheses.✓ Proved
- \[ = x^{2} \frac{d}{d x} \ln{\left(2 x \right)} + 2 x \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) \]constant algebraThe derivative of the constant 1/2 is 0. Simplify the expression by removing the zero term.✓ Proved
- \[ = 2 x \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) + \frac{x \frac{d}{d x} 2 x}{2} \]chainApply the chain rule to the logarithm.✓ Proved
- \[ = 2 x \left(\ln{\left(2 x \right)} - \frac{1}{2}\right) + x \]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
- \[ = 2 x \ln{\left(2 x \right)} \]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
| Line | Status | Checked by | Detail |
|---|---|---|---|
| 1 | ✓ Proved | sympy 1.14.0 | line 1 is the problem as stated |
| 2 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| 9 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| 10 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| 11 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| 12 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| answer | ✓ Proved | sympy 1.14.0 | final line against the stated answer: simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| answer, a second way | ✓ Proved | sympy 1.14.0 | SymPy differentiated f directly and got the stated answer |
Reviewers
deepseek-r1:70b: passgpt-oss:20b: passqwen3.6:27b-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 2026-09-20qwen3.6:27b-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 2026-09-20qwen3.6:27b-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 2026-09-19gpt-oss:20b: pass 2026-09-19qwen3.6:27b-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 2026-09-19gpt-oss:20b: pass 2026-09-19qwen3.6:27b-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 2026-09-18gpt-oss:20b: pass 2026-09-18deepseek-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.