Quote by Orion1
As stated by Wikipedia, the Friedmann equations are derived from General Relativity, not from Newtonian Mechanics. If you are interested in how these equations were derived, I recommend reading Friedmann's actual papers themselves, they are listed in reference 1 below, at the end of page in Reference as well as most of the important equations.
Reference:
Friedmann equations  Wikipedia

Yes, but for people who doesn't have the level
there is another way to get them, you can arrive by using Newtonian Mechanics, and when finally you have the constant then you have to compare with the real one and then you substitute your constant by the one that appears in the original one. That's the way I was asking for.
Thanks!