Derivative of \( \displaystyle x \ln{\left(3 x + 2 \right)} - x + \frac{2 \ln{\left(3 x + 2 \right)}}{3} \)
Problem 2.254 · hard Beautiful
Differentiate \( \displaystyle f(x) = x \ln{\left(3 x + 2 \right)} - x + \frac{2 \ln{\left(3 x + 2 \right)}}{3} \).
- \[ \frac{d}{d x} \left(x \ln{\left(3 x + 2 \right)} - x + \frac{2 \ln{\left(3 x + 2 \right)}}{3}\right) \]sumStart with the derivative of the entire expression.✓ Proved
- \[ = - \frac{d}{d x} x + \frac{d}{d x} x \ln{\left(3 x + 2 \right)} + \frac{d}{d x} \frac{2 \ln{\left(3 x + 2 \right)}}{3} \]sumApply the sum rule to separate the terms.✓ Proved
- \[ = \frac{d}{d x} x \ln{\left(3 x + 2 \right)} + \frac{d}{d x} \frac{2 \ln{\left(3 x + 2 \right)}}{3} - 1 \]derivativeDifferentiate the second term.✓ Proved
- \[ = \frac{d}{d x} x \ln{\left(3 x + 2 \right)} + \frac{2 \frac{d}{d x} \ln{\left(3 x + 2 \right)}}{3} - 1 \]constant-multiplePull out the constant factor from the third term.✓ Proved
- \[ = x \frac{d}{d x} \ln{\left(3 x + 2 \right)} + \ln{\left(3 x + 2 \right)} \frac{d}{d x} x + \frac{2 \frac{d}{d x} \ln{\left(3 x + 2 \right)}}{3} - 1 \]productApply the product rule to the first term.✓ Proved
- \[ = x \frac{d}{d x} \ln{\left(3 x + 2 \right)} + \ln{\left(3 x + 2 \right)} + \frac{2 \frac{d}{d x} \ln{\left(3 x + 2 \right)}}{3} - 1 \]derivative algebraDifferentiate the first part of the product. Simplify the multiplication by 1.✓ Proved
- \[ = \left(x + \frac{2}{3}\right) \frac{d}{d x} \ln{\left(3 x + 2 \right)} + \ln{\left(3 x + 2 \right)} - 1 \]algebraGroup the terms involving the derivative of the logarithm.✓ Proved
- \[ = \frac{3 \left(x + \frac{2}{3}\right)}{3 x + 2} + \ln{\left(3 x + 2 \right)} - 1 \]chainApply the chain rule to the logarithm.✓ Proved
- \[ = \ln{\left(3 x + 2 \right)} \]algebra simplify simplifyDistribute the 3 and simplify the numerator. Simplify the fraction. Final simplification.✓ Proved
Answer \( \log{\left(3 x + 2 \right)} \)
✓ 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 |
| 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 undefined where 3*x + 2 = 0 |
| 10 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 3*x + 2 = 0 |
| 11 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| 12 | ✓ 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: passdeepseek-r1:70b: 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 transformations performed.
Every verdict on record (12)
qwen3.6:27b-mlx: pass 2026-09-20 — The solution correctly applies differentiation rules step-by-step, adhering to the one-change-per-step constraint. All labels are appropriate for the transformations performed.gpt-oss:20b: pass 2026-09-20qwen3.6:27b-mlx: pass 2026-09-20 — 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 2026-09-20qwen3.6:27b-mlx: pass 2026-09-19 — The solution correctly applies differentiation rules step-by-step, adhering to the single-change constraint and using valid labels from the fixed vocabulary.deepseek-r1:70b: pass 2026-09-19gpt-oss:20b: pass 2026-09-19qwen3.6:27b-mlx: pass 2026-09-19 — 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.deepseek-r1:70b: pass 2026-09-19gpt-oss:20b: pass 2026-09-19gpt-oss:20b: pass 2026-09-17deepseek-r1:70b: pass 2026-09-17
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 2026-09-26 with SymPy 1.14.0.