Derivative of \( \displaystyle \left(x + \frac{1}{4}\right) e^{4 x + 2} \)
Problem 2.1224 · medium
Differentiate \( \displaystyle f(x) = \left(x + \frac{1}{4}\right) e^{4 x + 2} \).
- \[ \frac{d}{d x} \left(x + \frac{1}{4}\right) e^{4 x + 2} \]derivativeStart with the derivative of the function.✓ Proved
- \[ = \frac{d}{d x} x e^{4 x + 2} + \frac{d}{d x} \frac{e^{4 x + 2}}{4} \]sumApply the sum rule.✓ Proved
- \[ = \frac{d}{d x} x e^{4 x + 2} + \frac{\frac{d}{d x} e^{4 x + 2}}{4} \]constant-multipleApply the constant multiple rule to the second term.✓ Proved
- \[ = x \frac{d}{d x} e^{4 x + 2} + e^{4 x + 2} \frac{d}{d x} x + \frac{\frac{d}{d x} e^{4 x + 2}}{4} \]productApply the product rule to the first term.✓ Proved
- \[ = x \frac{d}{d x} e^{4 x + 2} + e^{4 x + 2} + \frac{\frac{d}{d x} e^{4 x + 2}}{4} \]derivativeDifferentiate x.✓ Proved
- \[ = 4 x e^{4 x + 2} + 2 e^{4 x + 2} \]chain algebra algebraApply the chain rule to the exponential terms. Simplify the coefficients. Combine like terms.✓ Proved
- \[ = \left(4 x + 2\right) e^{4 x + 2} \]algebraFactor out the exponential term.✓ Proved
Answer \( \left(4 x + 2\right) e^{4 x + 2} \)
✓ 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 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 4 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 5 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 6 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 7 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 8 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| 9 | ✓ Proved | sympy 1.14.0 | simplify(a - b) reduced to 0 |
| answer | ✓ Proved | sympy 1.14.0 | final line against the stated answer: simplify(a - b) reduced to 0 |
| answer, a second way | ✓ Proved | sympy 1.14.0 | SymPy differentiated f directly and got the stated answer |
Reviewers
gpt-oss:20b: fail (style) — Step 2 incorrectly labels the distributive expansion as a "sum" rule; it should be an "algebra" step. The rest of the steps are otherwise correct.qwen3.6:27b-mlx: pass
Every verdict on record (4)
qwen3.6:27b-mlx: pass 2026-09-29gpt-oss:20b: fail (style) 2026-09-29 — Step 2 incorrectly labels the distributive expansion as a "sum" rule; it should be an "algebra" step. The rest of the steps are otherwise correct.qwen3.6:27b-mlx: pass 2026-09-29gpt-oss:20b: fail (style) 2026-09-29 — Step 2 incorrectly labels the algebraic rewrite of (x+1/4)*exp(4*x+2) into x*exp(4*x+2)+(1/4)*exp(4*x+2) as a "sum" rule. It should be labeled "rewrite" since no differentiation rule is applied at that point.
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 2026-09-29 with SymPy 1.14.0.