Definite integrals
Problem 4.91 · medium
Evaluate \( \displaystyle \int_{1}^{2} 3 \sqrt{x} + 1 \, dx \).
- By the Fundamental Theorem of Calculus, Part 2, the integral is F(b) − F(a) for any antiderivative F.Reviewed
- \[ \frac{d}{d x} \left(2 x^{\frac{3}{2}} + x\right) = 3 \sqrt{x} + 1 \]F(x) = 2*x**(3/2) + x is an antiderivative: its derivative is the integrand.✓ Proved
- \[ - \left. x + 2 x^{\frac{3}{2}} \right|_{\substack{ x=1 }} + \left. 2 x^{\frac{3}{2}} + x \right|_{\substack{ x=2 }} = -1 + 4 \sqrt{2} \]F(b) − F(a).✓ Proved
Answer \( -1 + 4 \sqrt{2} \)
✓ Nihil obstat Lines: 2 proved, 1 reviewed. 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 | Reviewed | reviewers: gpt-oss:20b, qwen3.6:27b-mlx | a sentence; read, not computed |
| 2 | ✓ Proved | sympy 1.14.0 | simplify(lhs - rhs) reduced to 0 |
| 3 | ✓ Proved | sympy 1.14.0 | simplify(lhs - rhs) reduced to 0 |
| answer, a second way | ✓ Checked independently | sympy 1.14.0 + mpmath 1.3.0 | numerical quadrature (mpmath) gives the same value |
Reviewers
gpt-oss:20b: passqwen3.6:27b-mlx: pass — The solution correctly identifies the antiderivative and applies the Fundamental Theorem of Calculus. The algebraic evaluation is correct.
Every verdict on record (4)
qwen3.6:27b-mlx: pass 2026-09-26 — The solution correctly identifies the antiderivative and applies the Fundamental Theorem of Calculus. The algebraic evaluation is correct.gpt-oss:20b: pass 2026-09-26qwen3.6:27b-mlx: pass 2026-09-26 — The solution correctly identifies the antiderivative and applies the Fundamental Theorem of Calculus. The arithmetic is correct.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
generator:structured/definite_integral, checked 2026-09-26 with SymPy 1.14.0.