Derivative of \( \displaystyle 2 x \left(\ln{\left(4 x \right)} - 1\right) \)
Problem 2.985 · medium
Differentiate \( \displaystyle f(x) = 2 x \left(\ln{\left(4 x \right)} - 1\right) \).
- \[ \frac{d}{d x} 2 x \left(\ln{\left(4 x \right)} - 1\right) \]Start with the derivative of the function.✓ Proved
- \[ = 2 \frac{d}{d x} x \left(\ln{\left(4 x \right)} - 1\right) \]constant-multiplePull out the constant factor 2.✓ Proved
- \[ = 2 x \frac{d}{d x} \left(\ln{\left(4 x \right)} - 1\right) + 2 \left(\ln{\left(4 x \right)} - 1\right) \frac{d}{d x} x \]productApply the product rule.✓ Proved
- \[ = 2 x \frac{d}{d x} \left(\ln{\left(4 x \right)} - 1\right) + 2 \ln{\left(4 x \right)} - 2 \]derivativeDifferentiate the first part of the product.✓ Proved
- \[ = 2 x \left(- \frac{d}{d x} 1 + \frac{d}{d x} \ln{\left(4 x \right)}\right) + 2 \ln{\left(4 x \right)} - 2 \]sumDistribute the derivative over the subtraction.✓ Proved
- \[ = 2 x \frac{d}{d x} \ln{\left(4 x \right)} + 2 \ln{\left(4 x \right)} - 2 \]constantThe derivative of the constant 1 is 0.✓ Proved
- \[ = 2 \ln{\left(4 x \right)} + \frac{\frac{d}{d x} 4 x}{2} - 2 \]chainApply the chain rule to the logarithm.✓ Proved
- \[ = 2 \ln{\left(4 x \right)} \]derivative algebra algebra simplifyDifferentiate the inner function 4*x. Simplify the fraction. Simplify the product of x and 1/x. Combine the constant terms inside the parentheses.✓ Proved
Answer \( 2 \ln{\left(4 x \right)} \)
✓ 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)
qwen3.6:27b-mlx: pass 2026-09-27gpt-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. All labels are appropriate for the operations performed.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.