lean_workbook_plus_23900

Proved

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

Let $a,b$ be reals such that $(a+1)(a+b-1)=1$ .Prove that

(a^2+1)(b^2+1)\ge \frac{5}{2}

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_23900 (a b : ℝ) (h : (a + 1) * (a + b - 1) = 1) : (a^2 + 1) * (b^2 + 1) ≥ 5 / 2   :=  by sorry

Source