Derivative of \( \displaystyle - \frac{x^{2}}{2} - 2 x + \left(x^{2} + 4 x + 4\right) \ln{\left(x + 2 \right)} \)
Problem 2.1600 · hard
Differentiate \( \displaystyle f(x) = - \frac{x^{2}}{2} - 2 x + \left(x^{2} + 4 x + 4\right) \ln{\left(x + 2 \right)} \).
- \[ \frac{d}{d x} \left(- \frac{x^{2}}{2} - 2 x + \left(x^{2} + 4 x + 4\right) \ln{\left(x + 2 \right)}\right) \]derivativeStart with the derivative of the function.✓ Proved
- \[ = - \frac{d}{d x} 2 x + \frac{d}{d x} \left(- \frac{x^{2}}{2}\right) + \frac{d}{d x} \left(x^{2} + 4 x + 4\right) \ln{\left(x + 2 \right)} \]sumApply the sum rule.✓ Proved
- \[ = \left(x^{2} + 4 x + 4\right) \frac{d}{d x} \ln{\left(x + 2 \right)} + \ln{\left(x + 2 \right)} \frac{d}{d x} \left(x^{2} + 4 x + 4\right) - \frac{d}{d x} 2 x + \frac{d}{d x} \left(- \frac{x^{2}}{2}\right) \]productApply the product rule to the third term.✓ Proved
- \[ = \left(2 x + 4\right) \ln{\left(x + 2 \right)} + \left(x^{2} + 4 x + 4\right) \frac{d}{d x} \ln{\left(x + 2 \right)} - \frac{d}{d x} 2 x + \frac{d}{d x} \left(- \frac{x^{2}}{2}\right) \]derivativeDifferentiate the polynomial term.✓ Proved
- \[ = \left(2 x + 4\right) \ln{\left(x + 2 \right)} - \frac{d}{d x} 2 x + \frac{d}{d x} \left(- \frac{x^{2}}{2}\right) + \frac{x^{2} + 4 x + 4}{x + 2} \]derivativeDifferentiate the logarithm term.✓ Proved
- \[ = x + \left(2 x + 4\right) \ln{\left(x + 2 \right)} - \frac{d}{d x} 2 x + \frac{d}{d x} \left(- \frac{x^{2}}{2}\right) + 2 \]algebra algebraFactor the quadratic term. Simplify the fraction.✓ Proved
- \[ = \left(2 x + 4\right) \ln{\left(x + 2 \right)} \]derivative simplifyCompute the derivatives of the remaining terms. Combine like terms.✓ Proved
Answer \( 2 \left(x + 2\right) \ln{\left(x + 2 \right)} \)
✓ 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 undefined where x + 2 = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where x + 2 = 0 |
| 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. The labels accurately reflect the operations performed, and the final simplification is correct.
Every verdict on record (4)
qwen3.6:27b-mlx: pass 2026-10-05 — The solution correctly applies differentiation rules step-by-step, adhering to the one-change-per-step constraint. The labels accurately reflect the operations performed, and the final simplification is correct.gpt-oss:20b: pass 2026-10-05qwen3.6:27b-mlx: pass 2026-10-05 — The solution correctly applies differentiation rules and algebraic simplifications. Each step changes only one aspect of the expression, and the labels accurately reflect the operations performed.gpt-oss:20b: pass 2026-10-05
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 2026-10-05 with SymPy 1.14.0.