We have non-zero integers such that each one of them is divisible by the sum of the other numbers. Prove that the sum of all the given numbers is zero.
Problem 1501
Official solution
1. Let be the given non-zero integers, and let be the sum of these integers.
2. According to the problem, each is divisible by the sum of the other numbers. This can be written as:
3. This implies that for all . Let be an integer such that:
4. Rearranging the equation, we get:
5. Summing up all , we have:
6. Factoring out from the sum, we get:
7. If , we can divide both sides by :
8. Simplifying the right-hand side, we get:
9. Rearranging the equation, we obtain:
10. Since are integers, the only possible values for that satisfy this equation are and . However, this leads to a contradiction because if , then , which contradicts the given condition that all are non-zero.
11. Therefore, the assumption must be false, implying that .
The final answer is .