When \(a \ne 0\), there are two solutions to \(ax^2 + bx + c = 0\) and they are $$x = {-b \pm \sqrt{b^2-4ac} \over 2a}.$$ Add up the infinite sequence: $${1 \over 2} + {1 \over 3} + {1 \over 4} + ... $$ This can be written more compactly as: $$\sum_{n=2}^\infty {1 \over n}$$