Derivative of \( \displaystyle \frac{5 x^{2}}{4} - \frac{x}{2} + \left(- \frac{5 x^{2}}{2} + x - \frac{1}{10}\right) \ln{\left(5 x - 1 \right)} \)
Problem 2.2422 · hard Video
Differentiate \( \displaystyle f(x) = \frac{5 x^{2}}{4} - \frac{x}{2} + \left(- \frac{5 x^{2}}{2} + x - \frac{1}{10}\right) \ln{\left(5 x - 1 \right)} \).
- \[ \frac{d}{d x} \left(\frac{5 x^{2}}{4} - \frac{x}{2} + \left(- \frac{5 x^{2}}{2} + x - \frac{1}{10}\right) \ln{\left(5 x - 1 \right)}\right) \]derivativeStart with the derivative of the function.✓ Proved
- \[ = - \frac{d}{d x} \frac{x}{2} + \frac{d}{d x} \frac{5 x^{2}}{4} + \frac{d}{d x} \left(- \frac{5 x^{2}}{2} + x - \frac{1}{10}\right) \ln{\left(5 x - 1 \right)} \]sumApply the sum rule.✓ Proved
- \[ = \left(- \frac{5 x^{2}}{2} + x - \frac{1}{10}\right) \frac{d}{d x} \ln{\left(5 x - 1 \right)} + \ln{\left(5 x - 1 \right)} \frac{d}{d x} \left(- \frac{5 x^{2}}{2} + x - \frac{1}{10}\right) - \frac{d}{d x} \frac{x}{2} + \frac{d}{d x} \frac{5 x^{2}}{4} \]productApply the product rule to the third term.✓ Proved
- \[ = \left(1 - 5 x\right) \ln{\left(5 x - 1 \right)} + \left(- \frac{5 x^{2}}{2} + x - \frac{1}{10}\right) \frac{d}{d x} \ln{\left(5 x - 1 \right)} - \frac{d}{d x} \frac{x}{2} + \frac{d}{d x} \frac{5 x^{2}}{4} \]derivativeDifferentiate the polynomial part of the product.✓ Proved
- \[ = \left(1 - 5 x\right) \ln{\left(5 x - 1 \right)} - \frac{d}{d x} \frac{x}{2} + \frac{d}{d x} \frac{5 x^{2}}{4} + \frac{\left(- \frac{5 x^{2}}{2} + x - \frac{1}{10}\right) \frac{d}{d x} \left(5 x - 1\right)}{5 x - 1} \]chainApply the chain rule to the logarithm.✓ Proved
- \[ = \left(1 - 5 x\right) \ln{\left(5 x - 1 \right)} - \frac{d}{d x} \frac{x}{2} + \frac{d}{d x} \frac{5 x^{2}}{4} + \frac{5 \left(- \frac{5 x^{2}}{2} + x - \frac{1}{10}\right)}{5 x - 1} \]derivativeDifferentiate the inner function 5*x - 1.✓ Proved
- \[ = \left(1 - 5 x\right) \ln{\left(5 x - 1 \right)} - \frac{d}{d x} \frac{x}{2} + \frac{d}{d x} \frac{5 x^{2}}{4} + \frac{- \frac{25 x^{2}}{2} + 5 x - \frac{1}{2}}{5 x - 1} \]algebraMultiply the numerator by 5.✓ Proved
- \[ = \frac{5 x}{2} + \left(1 - 5 x\right) \ln{\left(5 x - 1 \right)} - \frac{1}{2} + \frac{- \frac{25 x^{2}}{2} + 5 x - \frac{1}{2}}{5 x - 1} \]derivativeDifferentiate the first two terms.✓ Proved
- \[ = \frac{5 x}{2} + \left(1 - 5 x\right) \ln{\left(5 x - 1 \right)} - \frac{1}{2} + \frac{- 25 x^{2} + 10 x - 1}{10 x - 2} \]algebra simplifySimplify the fraction by multiplying the numerator and denominator by 2. Distribute the 2 in the denominator.✓ Proved
Answer \( \left(1 - 5 x\right) \ln{\left(5 x - 1 \right)} \)
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. How we verify
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 undefined where 5*x - 1 = 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 5*x - 1 = 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 5*x - 1 = 0 |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 5*x - 1 = 0 |
| 9 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 5*x - 1 = 0 undefined where 10*x - 2 = 0 |
| 10 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 log is undefined for non-positive arguments undefined where 10*x - 2 = 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 |
| 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 algebraic simplifications in the final steps are valid, and the final result matches the stated answer.
Every verdict on record (6)
qwen3.6:27b-mlx: pass 2026-10-19 — The solution correctly applies differentiation rules step-by-step, adhering to the one-change-per-step constraint. The algebraic simplifications in the final steps are valid, and the final result matches the stated answer.gpt-oss:20b: pass 2026-10-19qwen3.6:27b-mlx: pass 2026-10-16 — The solution correctly applies differentiation rules step-by-step, adhering to the one-change-per-step constraint. The algebraic simplifications in the final steps are valid and lead to the correct result.gpt-oss:20b: fail (error) 2026-10-16 — The final expression contains an extra rational term that does not cancel; the derivative is not simplified to (1-5*x)*log(5*x-1).qwen3.6:27b-mlx: pass 2026-10-16 — The solution correctly applies differentiation rules step-by-step. Each step changes only one aspect of the expression, uses valid labels from the vocabulary, and the final simplification is algebraically correct.gpt-oss:20b: pass 2026-10-16
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 2026-10-19 with SymPy 1.14.0.