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Derivative of \( \displaystyle \left(x + \frac{1}{4}\right) e^{4 x + 2} \)

Problem 2.1224 · medium

Differentiate \( \displaystyle f(x) = \left(x + \frac{1}{4}\right) e^{4 x + 2} \).
  1. \[ \frac{d}{d x} \left(x + \frac{1}{4}\right) e^{4 x + 2} \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = \frac{d}{d x} x e^{4 x + 2} + \frac{d}{d x} \frac{e^{4 x + 2}}{4} \]
    sumApply the sum rule.✓ Proved
  3. \[ = \frac{d}{d x} x e^{4 x + 2} + \frac{\frac{d}{d x} e^{4 x + 2}}{4} \]
    constant-multipleApply the constant multiple rule to the second term.✓ Proved
  4. \[ = x \frac{d}{d x} e^{4 x + 2} + e^{4 x + 2} \frac{d}{d x} x + \frac{\frac{d}{d x} e^{4 x + 2}}{4} \]
    productApply the product rule to the first term.✓ Proved
  5. \[ = x \frac{d}{d x} e^{4 x + 2} + e^{4 x + 2} + \frac{\frac{d}{d x} e^{4 x + 2}}{4} \]
    derivativeDifferentiate x.✓ Proved
  6. \[ = 4 x e^{4 x + 2} + 2 e^{4 x + 2} \]
    chain algebra algebraApply the chain rule to the exponential terms. Simplify the coefficients. Combine like terms.✓ Proved
  7. \[ = \left(4 x + 2\right) e^{4 x + 2} \]
    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
LineStatusChecked byDetail
1✓ Provedsympy 1.14.0line 1 is the problem as stated
2✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
3✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
4✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
5✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
6✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
7✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
8✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
9✓ Provedsympy 1.14.0simplify(a - b) reduced to 0
answer✓ Provedsympy 1.14.0final line against the stated answer: simplify(a - b) reduced to 0
answer, a second way✓ Provedsympy 1.14.0SymPy 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 2026-09-29
  • gpt-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 2026-09-29
  • gpt-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.