2 3-13 = 3 * (12)+3 *1,1= 3 (122+32+). It is12+2.
Introduction to sum of squares
The sum of squares is the sum of squares of two or more numbers. The two series of books collect the elementary mathematics classics of all countries in the world in different historical periods. Most of them have the function of studying the historical materials of mathematics education, which makes up for the shortcomings of the current elementary mathematics textbooks, such as unsystematic, lack of depth and lack of background introduction.
Feng Keqin's Sum of Squares is one of them, which is divided into four chapters and an appendix. This book introduces some very complicated mathematical history, mathematical ideas and problem-solving methods about algebraic number theory.
Sum of squares, a mathematical term, is defined as the sum of squares of two or more numbers, usually the sum of squares of some positive integers. The number of integers can be finite or infinite. Square sum formula: n(n+ 1)(2n+ 1)/6, that is, 1? +2? +3? +…+n？ =n(n+ 1)(2n+ 1)/6 .