Derivative of \( \displaystyle - \frac{x^{2} \ln{\left(x \right)}}{2} + \frac{x^{2}}{4} \)
Problem 2.1783 · hard Beautiful
Differentiate \( \displaystyle f(x) = - \frac{x^{2} \ln{\left(x \right)}}{2} + \frac{x^{2}}{4} \).
- \[ \frac{d}{d x} \left(- \frac{x^{2} \ln{\left(x \right)}}{2} + \frac{x^{2}}{4}\right) \]derivativeStart with the derivative of the function.✓ Proved
- \[ = \frac{d}{d x} \frac{x^{2}}{4} + \frac{d}{d x} \left(- \frac{x^{2} \ln{\left(x \right)}}{2}\right) \]sum constant-multipleApply the sum rule. Pull out the constant factors.✓ Proved
- \[ = \frac{\frac{d}{d x} x^{2}}{4} - \frac{\frac{d}{d x} x^{2} \ln{\left(x \right)}}{2} \]constant-multipleSeparate the constants from the derivatives.✓ Proved
- \[ = - \frac{x^{2} \frac{d}{d x} \ln{\left(x \right)}}{2} - \frac{\ln{\left(x \right)} \frac{d}{d x} x^{2}}{2} + \frac{\frac{d}{d x} x^{2}}{4} \]productApply the product rule to the first term.✓ Proved
- \[ = - x \ln{\left(x \right)} \]derivative algebra algebra simplifyDifferentiate the individual components. Simplify the terms inside the parentheses and the second term. Distribute the constant -1/2. Combine like terms.✓ Proved
Answer \( - x \ln{\left(x \right)} \)
✓ 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
| 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 |
| 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
gpt-oss:20b: passqwen3.6:27b-mlx: pass — The solution correctly applies differentiation rules step-by-step, adhering to the one-change-per-step constraint. All labels are appropriate for the operations performed.
Every verdict on record (4)
gpt-oss:20b: pass 2026-10-07qwen3.6:27b-mlx: pass 2026-10-07 — The solution correctly applies differentiation rules step-by-step, adhering to the one-change-per-step constraint. All labels are appropriate for the operations performed.gpt-oss:20b: pass 2026-10-07qwen3.6:27b-mlx: pass 2026-10-07 — The solution correctly applies differentiation rules step-by-step, adhering to the one-change-per-step constraint. All labels are appropriate for the operations performed.
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 2026-10-07 with SymPy 1.14.0.