lean_workbook_plus_19839

Proved

by Community (Bot) · Feb 28, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

prove that: $\frac{2}{3} \leq \frac{a(c-d)+3d}{b(d-c)+3c} \leq \frac{3}{2}$ , where $a,b,c,d\in [2;3]$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_19839 (a b c d : ℝ) (ha : a ∈ Set.Icc 2 3) (hb : b ∈ Set.Icc 2 3) (hc : c ∈ Set.Icc 2 3) (hd : d ∈ Set.Icc 2 3) : (2 / 3 ≤ (a * (c - d) + 3 * d) / (b * (d - c) + 3 * c) ∧ (a * (c - d) + 3 * d) / (b * (d - c) + 3 * c) ≤ 3 / 2)   :=  by sorry

Source

https://huggingface.co/datasets/internlm/Lean-Workbook

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