Derivative of \( \displaystyle \left(4 - x\right) e^{x - 3} \)
Problem 2.948 · medium
Differentiate \( \displaystyle f(x) = \left(4 - x\right) e^{x - 3} \).
- \[ \frac{d}{d x} \left(4 - x\right) e^{x - 3} \]Start with the derivative of the function.✓ Proved
- \[ = \left(4 - x\right) \frac{d}{d x} e^{x - 3} + e^{x - 3} \frac{d}{d x} \left(4 - x\right) \]productApply the product rule.✓ Proved
- \[ = \left(4 - x\right) \frac{d}{d x} e^{x - 3} - e^{x - 3} \frac{d}{d x} x + \frac{d}{d x} 4 \]sumDifferentiate the terms in the first part of the product rule.✓ Proved
- \[ = \left(4 - x\right) \frac{d}{d x} e^{x - 3} - e^{x - 3} \]derivative simplifyEvaluate the derivatives of the individual terms. Simplify the expression.✓ Proved
- \[ = \left(4 - x\right) e^{x - 3} \frac{d}{d x} \left(x - 3\right) - e^{x - 3} \]chainApply the chain rule to the exponential term.✓ Proved
- \[ = \left(4 - x\right) e^{x - 3} - e^{x - 3} \]derivative simplifyEvaluate the derivative of the inner function. Simplify the expression.✓ Proved
- \[ = \left(3 - x\right) e^{x - 3} \]algebra simplifyFactor out the common exponential term. Combine like terms.✓ Proved
Answer \( \left(3 - x\right) e^{x - 3} \)
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.
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 |
| 10 | ✓ 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: inconclusive — reviewer response could not be parsed: { "verdict": "fail", "severity": "error", "notes": "Step 3 applies the sum rule to the derivative of (4-x) but leaves the second term of the product rule untouched. This violates the 'one change
Every verdict on record (4)
qwen3.6:27b-mlx: inconclusive 2026-09-27 — reviewer response could not be parsed: { "verdict": "fail", "severity": "error", "notes": "Step 3 applies the sum rule to the derivative of (4-x) but leaves the second term of the product rule untouched. This violates the 'one changegpt-oss:20b: pass 2026-09-27qwen3.6:27b-mlx: fail (error) 2026-09-27 — Step 3 applies the sum rule to the derivative of (4-x) but leaves the second term of the product rule untouched, violating the 'one rule per step' constraint. It mixes differentiation of the first factor with the existing structure of the product rule expansion.gpt-oss:20b: pass 2026-09-27
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 2026-09-27 with SymPy 1.14.0.