Consider x2 + ax – 1 = 0,For the quadratic equation to have real roots D ≥ 0
Here a = 1, b = a and c = 1
In the given equation D = a2 – 4 ≥ o
⇒ a2 ≥ 4
So for all the real values of ‘a’ which are greater than or equal to 2 and – 2 the equation will have the real roots.