Four-color conjecture, one of the three major mathematical problems in modern world, was put forward in Britain. 1852, when Francis guthrie, who graduated from London University, came to a scientific research institute to do map coloring, he found an interesting phenomenon: "It seems that every map can be colored in four colors, which makes countries with the same border have different colors." Can this conclusion be strictly proved by mathematical methods? He and his younger brother Grace, who is studying in university, decided to give it a try. The manuscripts and papers used by the two brothers to prove this problem have been piled up, but the research work has not progressed.

Goldbach is a German middle school teacher and a famous mathematician. Born in 1690, 1725 was elected as an academician of the Academy of Sciences in Petersburg, Russia. 1742, Goldbach found in teaching that every even number not less than 6 is the sum of two prime numbers (numbers that can only be divisible by themselves).

Fermat's last theorem. Expressed in mathematical language is: an equation in the form of xn +yn =zn, when n is greater than 2, there is no positive integer solution.