e3arabi
المصدر: "Basic Mathematics: Teach Yourself" by Alan Graham and Patricia Barnes-Svarney "Mathematics: Its Content, Methods and Meaning" by A.N. Kolmogorov, A.P. Yushkevich, and Jean-Michel Kantor "The Art of Problem Solving, Volume 1: The Basics" by Sandor Lehoczky and Richard Rusczyk