add Mathematical

[adalbertobrant]

I've just added a mathematical folder for beginners.

[OpenGuideAdmin]

Hi, @adalbertobrant ,you have been invited as a member, join the org and help out by reviewing code if you want ! And create more issues !

[adalbertobrant]

Many thanks my friend, I would like to join the openGuide Team.

[HenrySundlie]

would this be a good place to add a function to factor quadratics?