Math chapter in Getting Started

I checked this out, but I haven’t done anything with it yet.
Rafael, perhaps you might like to update this chapter? Having done the Math
Guide, you would probably know what changes, if any, are necessary. Note:
this chapter (like all the chapters) does not need to cover everything, old
or new. For example, some examples and other details could be left out, or
some topics mentioned with a referral to the Math Guide.

Thanks!
Jean