According to the quadratic formula, the roots of a quadratic equation can be solved by:
x = [-b +- sqrt(b^2 - 4ac)]/2a
This formula can give us at most of 2 roots. Why?
It can only be either x = [-b + sqrt(b^2 - 4ac)]/2a or x = [-b - sqrt(b^2 - 4ac)]/2a
