lean_workbook_plus_14811

Proved

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

Let $a,b,c\in \mathbb{R}$ with $a+b-c=5,a-b+c=7.$ Calculated ${{a}^{2}}+{{b}^{2}}+{{c}^{2}}-2bc.$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_14811 (a b c : ℝ) (h₁ : a + b - c = 5) (h₂ : a - b + c = 7) : a^2 + b^2 + c^2 - 2 * b * c = 37   :=  by sorry

Source