pls answer.
Rearrange as
4x^2 + kx + 9 = 0
Will have non-real roors when the discriminant < 0
k^2 - 4 * 4 * 9 < 0
k^2 - 144 < 0
k^2 < 144
This will be true when k is on the interval ( -12 , 12)
