Derivative of \( \displaystyle \frac{\ln{\left(\ln{\left(4 x - 3 \right)} \right)}}{4} \)
Problem 2.1418 · hard
Differentiate \( \displaystyle f(x) = \frac{\ln{\left(\ln{\left(4 x - 3 \right)} \right)}}{4} \).
- \[ \frac{d}{d x} \frac{\ln{\left(\ln{\left(4 x - 3 \right)} \right)}}{4} \]constant-multipleApply the constant multiple rule.✓ Proved
- \[ = \frac{\frac{d}{d x} \ln{\left(\ln{\left(4 x - 3 \right)} \right)}}{4} \]chainApply the chain rule to the outer logarithm.✓ Proved
- \[ = \frac{\frac{d}{d x} \ln{\left(4 x - 3 \right)}}{4 \ln{\left(4 x - 3 \right)}} \]chainApply the chain rule to the inner logarithm.✓ Proved
- \[ = \frac{\frac{d}{d x} \left(4 x - 3\right)}{4 \left(4 x - 3\right) \ln{\left(4 x - 3 \right)}} \]chainApply the chain rule to the innermost linear term.✓ Proved
- \[ = \frac{1}{\left(4 x - 3\right) \ln{\left(4 x - 3 \right)}} \]simplify simplifyEvaluate the derivative of the linear term. Simplify the final expression.✓ Proved
Answer \( \frac{1}{\left(4 x - 3\right) \ln{\left(4 x - 3 \right)}} \)
Mind the domain. The answer is also defined on (3/4, 1), where f(x) is not. Substituting there gives a number that is not a slope of f.
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. The reviewers disagree about how one step is explained; every verdict is in the receipt.
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 undefined where log(4*x - 3) = 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where log(4*x - 3) = 0 undefined where 4*x - 3 = 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 4*x - 3 = 0 undefined where log(4*x - 3) = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 4*x - 3 = 0 undefined where log(4*x - 3) = 0 |
| 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 undefined where 4*x - 3 = 0 undefined where log(4*x - 3) = 0 |
| answer, a second way | ✓ Proved | sympy 1.14.0 | SymPy differentiated f directly and got the stated answer |
Reviewers
gpt-oss:20b: fail (error) — Step 2 incorrectly applies the chain rule: the derivative of log(log(4*x-3)) should be 1/log(log(4*x-3)) times the derivative of log(4*x-3), not 1/log(4*x-3). This mistake propagates through the subsequent steps.qwen3.6:27b-mlx: pass
Every verdict on record (4)
qwen3.6:27b-mlx: pass 2026-10-03gpt-oss:20b: fail (error) 2026-10-03 — Step 2 incorrectly applies the chain rule: the derivative of log(log(4*x-3)) should be 1/log(log(4*x-3)) times the derivative of log(4*x-3), not 1/log(4*x-3). This mistake propagates through the subsequent steps.qwen3.6:27b-mlx: pass 2026-10-03gpt-oss:20b: fail (style) 2026-10-03 — Step 2 is incorrectly labeled as "chain"; it merely applies the constant‑multiple rule (or is a simple algebraic rewrite), not a chain rule. The correct label would be "constant‑multiple" or "algebra".
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 2026-10-03 with SymPy 1.14.0.