I understand that when roots a quadratic equation is found, we are essentially finding values of x for which y or f(x) is zero. But what how does it help us? I mean why are we only interested in values of x which makes y zero. e.g. quadratic formula for finding roots could only be used for finding values of x for which y is zero but it won't help us if we want to know values of x for which y is 2. Will it? Likewise, while solving differential equations we are only interested in those values which make the differential function equal to zero.

Regards

PG