Discriminant:In a quadratic equation $ax^2 + bx + c = 0$, it is given by $\Delta = b^2 - 4ac$ and determines the nature of the roots.
Complex Roots:Roots that occur when the discriminant ($b^2 - 4ac$) is negative, resulting in non-real solutions of a quadratic equation.
Completing The Square: A method used to solve a quadratic equation by rewriting it in the form $(x-h)^2 = k$, making it easier to solve for x.