Derivative of \( \displaystyle 3 x \ln{\left(x \right)} - 3 x \)
Problem 2.1937 · hard Beautiful
Differentiate \( \displaystyle f(x) = 3 x \ln{\left(x \right)} - 3 x \).
- \[ \frac{d}{d x} \left(3 x \ln{\left(x \right)} - 3 x\right) \]derivativeStart with the derivative of the function.✓ Proved
- \[ = - \frac{d}{d x} 3 x + \frac{d}{d x} 3 x \ln{\left(x \right)} \]sumApply the sum rule.✓ Proved
- \[ = - \frac{d}{d x} 3 x + 3 \frac{d}{d x} x \ln{\left(x \right)} \]constant-multipleFactor out the constant 3.✓ Proved
- \[ = 3 x \frac{d}{d x} \ln{\left(x \right)} + 3 \ln{\left(x \right)} \frac{d}{d x} x - \frac{d}{d x} 3 x \]productApply the product rule to the first term.✓ Proved
- \[ = 3 \ln{\left(x \right)} - \frac{d}{d x} 3 x + 3 \]derivative algebra algebraDifferentiate the individual components. Simplify the expression inside the parentheses. Distribute the 3 into the parentheses.✓ Proved
- \[ = 3 \ln{\left(x \right)} - 3 \frac{d}{d x} x + 3 \]constant-multipleFactor out the 3 from the second term.✓ Proved
- \[ = 3 \ln{\left(x \right)} \]derivative algebra simplifyDifferentiate the remaining term. Simplify the expression. Combine the constant terms.✓ Proved
Answer \( 3 \ln{\left(x \right)} \)
✓ 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 |
| 10 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments |
| 11 | ✓ 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
Every verdict on record (4)
gpt-oss:20b: pass 2026-10-09qwen3.6:27b-mlx: pass 2026-10-09qwen3.6:27b-mlx: pass 2026-10-09 — 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 2026-10-09
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 2026-10-09 with SymPy 1.14.0.