(a+b)²-(a-b)²= 4ab
http://dmentrard.free.fr/GEOGEBRA/Maths/Export5/4abMD.html
[url=http://dmentrard.free.fr/GEOGEBRA/Maths/Export5/4abMD.html]http://dmentrard.free.fr/GEOGEBRA/Maths/Export5/4abMD.html[/url]
Information: (a+b)²-(a-b)²= 4ab