Find the interval(s) for such that the equation has at least one real solution. x^2 + bx + 9 = 0

Question

Find the interval(s) for such that the equation has at least one real solution. x^2 + bx + 9 = 0.

Answer 1

Using the Quadratic Formula, the solutions are complex it b < 6. There for the functions has at least one real (actually it has two reals that are twins!) when b = 0 or b > 6.