Question

Write the set of values of k for which the quadratic equation has 2x² + kx + 8 = 0 has real roots.

Answer 1

To have the real roots D = b² – 4ac ≥ 0 

Here a = 2, b = k and c = 8 

D = k² – 4 x 2 x 8 ≥ 0 

⇒ K²≥ 64 

⇒ K ≥ 8 

So for all the values of k greater than or equal to 8 and – 8, the given quadratic equation will have real roots.