Derivative of \( \displaystyle - \frac{x^{2}}{2} + 3 x + \left(x^{2} - 6 x + 9\right) \ln{\left(x - 3 \right)} \)
Problem 2.2072 · hard
Differentiate \( \displaystyle f(x) = - \frac{x^{2}}{2} + 3 x + \left(x^{2} - 6 x + 9\right) \ln{\left(x - 3 \right)} \).
- \[ \frac{d}{d x} \left(- \frac{x^{2}}{2} + 3 x + \left(x^{2} - 6 x + 9\right) \ln{\left(x - 3 \right)}\right) \]sumStart with the derivative of the entire function.✓ Proved
- \[ = \frac{d}{d x} 3 x + \frac{d}{d x} \left(- \frac{x^{2}}{2}\right) + \frac{d}{d x} \left(x^{2} - 6 x + 9\right) \ln{\left(x - 3 \right)} \]sumApply the sum rule to separate the terms.✓ Proved
- \[ = \left(x^{2} - 6 x + 9\right) \frac{d}{d x} \ln{\left(x - 3 \right)} + \ln{\left(x - 3 \right)} \frac{d}{d x} \left(x^{2} - 6 x + 9\right) + \frac{d}{d x} 3 x + \frac{d}{d x} \left(- \frac{x^{2}}{2}\right) \]productApply the product rule to the third term.✓ Proved
- \[ = \left(2 x - 6\right) \ln{\left(x - 3 \right)} + \left(x^{2} - 6 x + 9\right) \frac{d}{d x} \ln{\left(x - 3 \right)} + \frac{d}{d x} 3 x + \frac{d}{d x} \left(- \frac{x^{2}}{2}\right) \]derivativeDifferentiate the polynomial part of the product.✓ Proved
- \[ = \left(2 x - 6\right) \ln{\left(x - 3 \right)} + \frac{d}{d x} 3 x + \frac{d}{d x} \left(- \frac{x^{2}}{2}\right) + \frac{x^{2} - 6 x + 9}{x - 3} \]derivativeDifferentiate the logarithmic part.✓ Proved
- \[ = - x + \left(2 x - 6\right) \ln{\left(x - 3 \right)} + 3 + \frac{x^{2} - 6 x + 9}{x - 3} \]derivativeEvaluate the derivatives of the first two terms.✓ Proved
- \[ = \left(2 x - 6\right) \ln{\left(x - 3 \right)} \]algebra simplify algebra simplifyRecognize that x**2 - 6*x + 9 is (x - 3)**2. Simplify the fraction. Expand the simplified term. Combine all terms to get the final result.✓ Proved
Answer \( 2 \left(x - 3\right) \ln{\left(x - 3 \right)} \)
✓ 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 - 3 = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where x - 3 = 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where x - 3 = 0 |
| 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 |
| 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 the sum, product, and chain rules in separate steps. The algebraic simplifications are valid and clearly labeled.
Every verdict on record (4)
gpt-oss:20b: pass 2026-10-11qwen3.6:27b-mlx: pass 2026-10-11 — The solution correctly applies the sum, product, and chain rules in separate steps. The algebraic simplifications are valid and clearly labeled.gpt-oss:20b: pass 2026-10-11qwen3.6:27b-mlx: pass 2026-10-11 — The solution correctly applies differentiation rules step-by-step, adhering to the one-change-per-step constraint. The algebraic simplifications and derivative evaluations are accurate and properly labeled.
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 2026-10-11 with SymPy 1.14.0.