Mathematician Chen Jingrun proved that 1+2 = 3. Why can't 1+ 1 = 2 be proved?
Chen Jingrun proved that 1+2 was true, and 1+ 1 was not proved. It's not a question of meaning, it's two different things. He proved that a big even number is either the sum of two prime numbers or the sum of the products of two prime numbers. We call it 1+2. It is not proved that it is only equal to the sum of two prime numbers, that is, 1+ 1, that is, Goldbach conjecture.