Evaluating a quadratic at five halves

Proved

WorkbookSource.problem_16924

by wamlart · Sep 12, 2026 · Mathlib 0df444a (Lean v4.33.1)

lean-workbooksource-checked

FF1 $f(x) = 4x+x^2+ 2x$ Find $f$ $(\frac{5}{2})$

Source: InternLM Lean-Workbook, record lean_workbook_16924 (Apache-2.0). The complete source proposition and explicit variable declarations are preserved.

Preamble

import Mathlib
open Real Nat

Formal statement

theorem WorkbookSource.problem_16924 (f : ℝ → ℝ) (f_def : ∀ x, f x = 4 * x + x ^ 2 + 2 * x) : f (5 / 2) = 85 / 4  :=  by sorry

Source

https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, record lean_workbook_16924; Apache-2.0

View graph