Integral of \( \displaystyle \left(2 x - 1\right) e^{1 - 2 x} \)
Problem 4.143 · medium
Find \( \displaystyle \int \left(2 x - 1\right) e^{1 - 2 x} \, dx \). (Omit the constant of integration.)
- \[ \int \left(2 x - 1\right) e^{1 - 2 x}\, dx \]integralStart with the integral of the given function.✓ Proved
- \[ = \int \left(2 x e^{1 - 2 x} - e^{1 - 2 x}\right)\, dx \]linearityDistribute the exponential term.✓ Proved
- \[ = 2 \int x e^{1 - 2 x}\, dx - \int e^{1 - 2 x}\, dx \]linearitySplit the integral into two parts.✓ Proved
- \[ = \frac{e^{1 - 2 x}}{2} + 2 \int x e^{1 - 2 x}\, dx \]antiderivativeEvaluate the second integral.✓ Proved
- \[ = - x e^{1 - 2 x} + \frac{e^{1 - 2 x}}{2} - 2 \int \left(- \frac{e^{1 - 2 x}}{2}\right)\, dx \]partsApply integration by parts to the first integral.✓ Proved
- \[ = - x e^{1 - 2 x} + \frac{e^{1 - 2 x}}{2} + \int e^{1 - 2 x}\, dx \]algebra algebraSimplify the expression inside the parentheses. Distribute the 2.✓ Proved
- \[ = - x e^{1 - 2 x} \]antiderivative simplifyEvaluate the remaining integral. Combine the terms.✓ Proved
Answer \( - x e^{1 - 2 x} + C \)
✓ 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 the stated antiderivative back to the integrand |
Reviewers
gpt-oss:20b: passqwen3.6:27b-mlx: pass — The solution correctly applies linearity, integration by parts, and antiderivative rules in a step-by-step manner. Each step changes only one aspect of the expression and uses valid labels from the fixed vocabulary.
Every verdict on record (4)
qwen3.6:27b-mlx: pass 2026-09-29 — The solution correctly applies linearity, integration by parts, and antiderivative rules in a step-by-step manner. Each step changes only one aspect of the expression and uses valid labels from the fixed vocabulary.gpt-oss:20b: pass 2026-09-29qwen3.6:27b-mlx: pass 2026-09-29 — The solution correctly applies linearity, integration by parts, and antiderivative rules in a step-by-step manner. Each step changes only one aspect of the expression and uses valid labels from the fixed vocabulary.gpt-oss:20b: pass 2026-09-29
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.