You have to get first the discrimant of the equation. The formula for this is b^2 -4ac.
If the discirminant is ewual to zero, the nature of roots is real, rational and equal. If the discriminant is greater tha zero and has a perfect square, the nature is real, rational and unequal. If the discriminant is greater than zero but doesn't have a perfect square, the nature is real, irrational and unequal. And if the discriminant is less than zero or is negative, the roots are not real.