You had a right approach, but we want an inequality . . .
(a) A quadratic has two real roots if its discriminant is positive: .Given that the equation has real roots,
(a) show that:
(b) Find the range of values of satisfying this inequality.
. . So we have: .
. . Divide by -4: .
(b) We have: .
. . Factor: .
The product of two factors is negative if they have opposite signs.
So there are two cases: