The value under the square root sign in the quadratic formula works out negative. What are the roots?

1. The quadratic formula takes the square root of an expression built from the coefficients. 2. That expression must be greater than or equal to zero for the roots to be real. 3. If the expression under the square root sign is less than zero, the roots are non-real. 4. Equal roots are the separate case where that expression works out to exactly zero. _Source: Siyavula Mathematics Grade 11 (Everything Maths, CC BY 4.0), Chapter 2: Equations and inequalities_