Derivative of \( \displaystyle \left(1 - x\right) e^{x} \)
Problem 2.869 · medium
Differentiate \( \displaystyle f(x) = \left(1 - x\right) e^{x} \).
- \[ \frac{d}{d x} \left(1 - x\right) e^{x} \]derivativeStart with the derivative of the function.✓ Proved
- \[ = \left(1 - x\right) \frac{d}{d x} e^{x} + e^{x} \frac{d}{d x} \left(1 - x\right) \]productApply the product rule.✓ Proved
- \[ = \left(1 - x\right) \frac{d}{d x} e^{x} + e^{x} \frac{d}{d x} 1 - e^{x} \frac{d}{d x} x \]algebraDistribute the derivative over the subtraction.✓ Proved
- \[ = \left(1 - x\right) \frac{d}{d x} e^{x} - e^{x} \]derivative algebraDifferentiate the terms inside the parentheses. Simplify the expression.✓ Proved
- \[ = \left(1 - x\right) e^{x} - e^{x} \]derivativeDifferentiate the exponential term.✓ Proved
- \[ = - x e^{x} \]algebra simplifyDistribute the exponential term. 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
| 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 |
| 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: passqwen3.6:27b-mlx: pass
Every verdict on record (4)
qwen3.6:27b-mlx: pass 2026-09-26gpt-oss:20b: pass 2026-09-26qwen3.6:27b-mlx: pass 2026-09-26 — The solution correctly applies the product rule, linearity of differentiation, and standard derivatives. Each step changes only one aspect of the expression and uses valid labels from the fixed vocabulary.gpt-oss:20b: pass 2026-09-26
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 2026-09-26 with SymPy 1.14.0.