Mathematics with Boris Trushin. Combinatorics: from scratch to the Olympiads. Trushin B.

Boris Trushin is the author of the same popular channel in subsidiary mathematics. This book is written based on videos created by the author in recent years. You will get acquainted with combinatorics closer and can understand this section of mathematics without any preliminary knowledge. You will go along an exciting route from the simplest tasks for the recharge of options, through Newton's beam and a triangle Pascal, to complex substantive tasks.

If you are looking for an understandable book in mathematics, so that you do not have to cram the theorem, but understand and feel them, then it is in front of you!