Derivative of \( \displaystyle - x \ln{\left(5 x + 2 \right)} + x - \frac{2 \ln{\left(5 x + 2 \right)}}{5} \)
Problem 2.947 · hard
Differentiate \( \displaystyle f(x) = - x \ln{\left(5 x + 2 \right)} + x - \frac{2 \ln{\left(5 x + 2 \right)}}{5} \).
- \[ \frac{d}{d x} \left(- x \ln{\left(5 x + 2 \right)} + x - \frac{2 \ln{\left(5 x + 2 \right)}}{5}\right) \]derivativeStart with the derivative of the function.✓ Proved
- \[ = \frac{d}{d x} x + \frac{d}{d x} \left(- x \ln{\left(5 x + 2 \right)}\right) + \frac{d}{d x} \left(- \frac{2 \ln{\left(5 x + 2 \right)}}{5}\right) \]sumApply the sum rule to separate the terms.✓ Proved
- \[ = \frac{d}{d x} x + \frac{d}{d x} \left(- x \ln{\left(5 x + 2 \right)}\right) - \frac{d}{d x} \frac{2 \ln{\left(5 x + 2 \right)}}{5} \]algebraRewrite the subtraction as addition of a negative term.✓ Proved
- \[ = \frac{d}{d x} x + \frac{d}{d x} \left(- x \ln{\left(5 x + 2 \right)}\right) - \frac{2 \frac{d}{d x} \ln{\left(5 x + 2 \right)}}{5} \]constant-multiplePull the constant factor out of the derivative.✓ Proved
- \[ = \frac{d}{d x} \left(- x \ln{\left(5 x + 2 \right)}\right) - \frac{2 \frac{d}{d x} \ln{\left(5 x + 2 \right)}}{5} + 1 \]derivativeDifferentiate the term x.✓ Proved
- \[ = \frac{d}{d x} \left(- x \ln{\left(5 x + 2 \right)}\right) + 1 - \frac{2 \frac{d}{d x} \left(5 x + 2\right)}{5 \left(5 x + 2\right)} \]chainApply the chain rule to the logarithm.✓ Proved
- \[ = \frac{d}{d x} \left(- x \ln{\left(5 x + 2 \right)}\right) + 1 - \frac{2}{5 x + 2} \]derivative algebraDifferentiate the inner linear function. Simplify the product of the constants and the fraction.✓ Proved
- \[ = - x \frac{d}{d x} \ln{\left(5 x + 2 \right)} + \ln{\left(5 x + 2 \right)} \frac{d}{d x} \left(- x\right) + 1 - \frac{2}{5 x + 2} \]productApply the product rule to the first term.✓ Proved
- \[ = - \frac{x \frac{d}{d x} \left(5 x + 2\right)}{5 x + 2} - \ln{\left(5 x + 2 \right)} + 1 - \frac{2}{5 x + 2} \]derivativeDifferentiate -x.✓ Proved
- \[ = - \frac{5 x}{5 x + 2} - \ln{\left(5 x + 2 \right)} + 1 - \frac{2}{5 x + 2} \]derivative algebraDifferentiate the inner part of the chain rule again. Simplify the term involving x.✓ Proved
- \[ = \frac{- 5 x - 2}{5 x + 2} - \ln{\left(5 x + 2 \right)} + 1 \]algebraCombine the fractions with the same denominator.✓ Proved
- \[ = - \ln{\left(5 x + 2 \right)} \]algebra simplifySimplify the fraction (-5x-2)/(5x+2) to -1. Final simplification.✓ Proved
Answer \( - \ln{\left(5 x + 2 \right)} \)
✓ 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 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 5*x + 2 = 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 5*x + 2 = 0 |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 5*x + 2 = 0 |
| 9 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 5*x + 2 = 0 |
| 10 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 5*x + 2 = 0 |
| 11 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 5*x + 2 = 0 |
| 12 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 5*x + 2 = 0 |
| 13 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 5*x + 2 = 0 |
| 14 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 5*x + 2 = 0 |
| 15 | ✓ 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 algebraic simplifications are valid.
Every verdict on record (4)
qwen3.6:27b-mlx: pass 2026-09-27 — 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 algebraic simplifications are valid.gpt-oss:20b: pass 2026-09-27qwen3.6:27b-mlx: pass 2026-09-27 — The solution correctly applies differentiation rules step-by-step, adhering to the one-change-per-step constraint and using valid labels from the fixed vocabulary.gpt-oss:20b: pass 2026-09-27
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 2026-09-27 with SymPy 1.14.0.