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Derivative of \( \displaystyle - x e^{x} + e^{x} \)

Problem 2.1935 · hard

Differentiate \( \displaystyle f(x) = - x e^{x} + e^{x} \).
  1. \[ \frac{d}{d x} \left(- x e^{x} + e^{x}\right) \]
    derivativeStart with the derivative of the function.✓ Proved
  2. \[ = \frac{d}{d x} \left(- x e^{x}\right) + \frac{d}{d x} e^{x} \]
    sumApply the sum rule.✓ Proved
  3. \[ = e^{x} + \frac{d}{d x} \left(- x e^{x}\right) \]
    derivativeDifferentiate the second term.✓ Proved
  4. \[ = e^{x} - \frac{d}{d x} x e^{x} \]
    constantFactor out the negative sign.✓ Proved
  5. \[ = - x \frac{d}{d x} e^{x} - e^{x} \frac{d}{d x} x + e^{x} \]
    productApply the product rule to the first term.✓ Proved
  6. \[ = - x e^{x} \]
    derivative algebra simplifyDifferentiate the components of the product rule. Distribute the negative sign. Combine like terms.✓ Proved
Answer \( - x e^{x} \)

✓ 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
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 4 incorrectly labels the constant‑multiple rule as "constant". The rule applied is factoring a constant outside a derivative, which belongs to the "constant‑multiple" category.
  • qwen3.6:27b-mlx: pass
Every verdict on record (4)
  • gpt-oss:20b: fail (style) 2026-10-09 — Step 4 incorrectly labels the constant‑multiple rule as "constant". The rule applied is factoring a constant outside a derivative, which belongs to the "constant‑multiple" category.
  • qwen3.6:27b-mlx: pass 2026-10-09
  • qwen3.6:27b-mlx: pass 2026-10-09
  • gpt-oss:20b: pass 2026-10-09

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 2026-10-09 with SymPy 1.14.0.