Around the quadratic law, reciprocity. Bibikov P.V., Akimov D.A., Belyaev D.A.

The brochure is devoted to such an important and difficult theorem of an elementary theory of numbers as Gaussian quadratic law of reciprocity. Five of its elementary evidence is given; In the way, such simpler, but fundamental facts as a small farm theorem and the Chinese theorem about the remains are versed. The presentation is illustrated by a large number of tasks of the Olympiad level.

for high school students, heads of mathematical circles, primary school students and all those interested in mathematics.