Composition of functions
Problem 13.355 · easy
Let \( \displaystyle f(x) = x^{2} - 5 \) and \( \displaystyle g(x) = 3 x + 1 \). Find \( \displaystyle (f \circ g)(3) \).
- (f∘g)(3) = f(g(3)): evaluate g first, then f at the result.Reviewed
- \[ \left. 3 x + 1 \right|_{\substack{ x=3 }} = 10 \]g(3).✓ Proved
- \[ \left. x^{2} - 5 \right|_{\substack{ x=10 }} = 95 \]f at that value.✓ Proved
Answer \( (f \circ g)(3) = 95 \)
✓ 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. How we verify
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 | g then f evaluated in floating point |
Reviewers
gpt-oss:20b: passqwen3.6:27b-mlx: pass
Every verdict on record (6)
qwen3.6:27b-mlx: pass 2026-10-19gpt-oss:20b: pass 2026-10-19qwen3.6:27b-mlx: pass 2026-10-16gpt-oss:20b: pass 2026-10-16qwen3.6:27b-mlx: pass 2026-10-16gpt-oss:20b: pass 2026-10-16
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/function_composition, checked 2026-10-19 with SymPy 1.14.0.