TDSM 8.5
From The Data Science Design Manual Wikia
[math]AC = CA \Rightarrow ACB = CAB[/math]
[math]BC = CB \Rightarrow ABC = ACB[/math]
[math]\Rightarrow CAB = ABC[/math] (1)
[math]AC = CA \Rightarrow BAC = BCA[/math]
[math]BC = CB \Rightarrow BCA = CBA[/math]
[math]\Rightarrow CBA = BAC[/math] (2)
(1) and (2) [math]\Rightarrow CAB+CBA = ABC+BAC \Leftrightarrow C(AB+BA) = (AB+BA)C[/math] (proved)
