Derivative of \( \displaystyle - 5 x + \left(5 x - 15\right) \ln{\left(x - 3 \right)} \)
Problem 2.2132 · hard Beautiful
Differentiate \( \displaystyle f(x) = - 5 x + \left(5 x - 15\right) \ln{\left(x - 3 \right)} \).
- \[ \frac{d}{d x} \left(- 5 x + \left(5 x - 15\right) \ln{\left(x - 3 \right)}\right) \]derivativeStart with the derivative of the function.✓ Proved
- \[ = \frac{d}{d x} \left(- 5 x\right) + \frac{d}{d x} \left(5 x - 15\right) \ln{\left(x - 3 \right)} \]sumApply the sum rule.✓ Proved
- \[ = \frac{d}{d x} \left(- 5 x\right) + \frac{d}{d x} \left(5 x \ln{\left(x - 3 \right)} - 15 \ln{\left(x - 3 \right)}\right) \]algebraDistribute the term (5*x - 15).✓ Proved
- \[ = \frac{d}{d x} \left(- 5 x\right) + \frac{d}{d x} 5 x \ln{\left(x - 3 \right)} - \frac{d}{d x} 15 \ln{\left(x - 3 \right)} \]sumApply the sum rule to the second part.✓ Proved
- \[ = \frac{d}{d x} 5 x \ln{\left(x - 3 \right)} - \frac{d}{d x} 15 \ln{\left(x - 3 \right)} - 5 \]constantDifferentiate the first term.✓ Proved
- \[ = 5 x \frac{d}{d x} \ln{\left(x - 3 \right)} + \ln{\left(x - 3 \right)} \frac{d}{d x} 5 x - \frac{d}{d x} 15 \ln{\left(x - 3 \right)} - 5 \]productApply the product rule to the second term.✓ Proved
- \[ = 5 x \frac{d}{d x} \ln{\left(x - 3 \right)} + 5 \ln{\left(x - 3 \right)} - \frac{d}{d x} 15 \ln{\left(x - 3 \right)} - 5 \]derivativeDifferentiate 5*x.✓ Proved
- \[ = \frac{5 x}{x - 3} + 5 \ln{\left(x - 3 \right)} - \frac{d}{d x} 15 \ln{\left(x - 3 \right)} - 5 \]logarithmicDifferentiate the natural logarithm.✓ Proved
- \[ = \frac{5 x}{x - 3} + 5 \ln{\left(x - 3 \right)} - 5 - \frac{15}{x - 3} \]derivative algebraDifferentiate the third term. Remove parentheses.✓ Proved
- \[ = 5 \ln{\left(x - 3 \right)} - 5 + \frac{5 x - 15}{x - 3} \]algebra algebraCombine the fractions. Factor the numerator.✓ Proved
- \[ = 5 \ln{\left(x - 3 \right)} \]algebra simplifySimplify the fraction. Combine the constant terms.✓ Proved
Answer \( 5 \ln{\left(x - 3 \right)} \)
✓ 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 |
| 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 undefined where x - 3 = 0 |
| 9 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where x - 3 = 0 |
| 10 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where x - 3 = 0 |
| 11 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where x - 3 = 0 |
| 12 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where x - 3 = 0 |
| 13 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where x - 3 = 0 |
| 14 | ✓ 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 single-change constraint. The algebraic simplification in the final steps is valid and clearly labeled.
Every verdict on record (4)
gpt-oss:20b: pass 2026-10-12qwen3.6:27b-mlx: pass 2026-10-12 — The solution correctly applies differentiation rules step-by-step, adhering to the single-change constraint. The algebraic simplification in the final steps is valid and clearly labeled.gpt-oss:20b: pass 2026-10-12qwen3.6:27b-mlx: pass 2026-10-12 — The solution correctly applies differentiation rules and algebraic simplifications in single-step increments. The labels used 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 2026-10-12 with SymPy 1.14.0.