a problem would be something like a+b+c=4,ab+ac+bc=22, abc=65. I don't really understand what you ment by an infinite number of solution, but thanks for taking the time to answer.
Found a solution: 1/n(n+1)=(1/n)-(1/n+1)
So It's (1-1/2)+(1/2-1/3)...
Everything cancels out to one
