Question

Write the set of values of 'a' for which the equation x² + ax – 1 = 0 has real roots.

Answer 1

The given quadric equation is  x² + ax − 1 = 0

Then find the value of a.

Here, a = 1, b = a and c = -1

As we know that `D = b^2 - 4ac`

Putting the value of a= 1, b = a and, c = -1

` = (a)^2 - 4 xx 1 xx -1`

` = a^2 + 4`

The given equation will have real roots, if D > 0_.

`a^2 + 4 >0`

⇒ `a^2 > - 4` which is true for all real values of a.

Therefore, for all real values of a, the given equation has real roots.