"1+2=3" is an addition formula, which needs no proof, because addition belongs to a postulate of mathematical system. The so-called postulate is to assume that it is right from the beginning, and then build the whole mathematical system on this basis. There is no need to prove postulate. On the other hand, if the postulate itself is not established, then the whole mathematical system based on it is wrong, which is obviously impossible.
Chen Jingrun put forward "1+2" (also known as "Chen's theorem") in 1966, and published a detailed proof of this theorem in 1973. Large-scale domestic reports began around 1978.
Chen Jingrun's "1+2" proof means:
In N=a+b,
A must be a prime number. (1)
B is the product of at most two prime numbers (2)
This proof pushes Brown's method one step further. More importantly, Chen Jingrun suggested that Brown's idea should stop here. If we follow this line of thinking, we should not prove "1+ 1".
In fact, it has been more than 40 years since Chen Jingrun proved "1+2", and no one can prove "1+ 1". Maybe Chen Jingrun is right, and Brown's road ends here. We need other methods to finally prove Goldbach's conjecture.
Extended data
Goldbach conjecture means that a man named Goldbach wrote to Euler, the great mathematical god at that time, saying that he had come up with a conjecture. There were several versions of this conjecture at that time, and now it is widely said that:
Any even number greater than 2,
It can be expressed as the sum of two prime numbers.
For example, 10=5+5, 100 = 3+97 ... Of course, the number of positive integers is infinite. No matter how hard you try, mathematicians must find ways to prove it. At the beginning of the 20th century, Norwegian mathematician Brown partially proved Goldbach's conjecture by screening method. His proposition is as follows:
All sufficiently large even numbers
Can be expressed as the sum of two numbers,
Each of these two number
It contains no more than 9 prime factors.
Suppose an even number n can be expressed as the sum of two numbers A and B, that is, N=a+b, where A and B are the products of n prime numbers, where n≤9. Brown abbreviated this proposition as "9+9", and he proposed that Goldbach conjecture is equivalent to "1+ 1" for his proposition.
Therefore, if someone can prove "1+ 1" according to Brown's thinking, it is equivalent to proving Goldbach's conjecture. Brown's method lit a beacon for mathematicians, so a group of people continued to improve according to this idea, and proved "7+7" and "6+6" all the way ... until 1965 was proved to be "1+3", and Chen Jingrun proved "1+2" on this basis.