A complex number is the sum of a real number and an imaginary number, written in the form .
A complex root is a complex number that, when used as an input () value of a function, results in an output () value of zero.
The discriminant is the part of the quadratic formula under the radical, . A positive discriminant suggests two real roots to the quadratic equation, a zero suggests one real root with multiplicity two, and a negative indicates two complex roots.
An imaginary number is a number that can be written as the product of a real number and .
The quadratic formula states that for any quadratic equation in the form , .
A real number is a number that can be plotted on a number line. Real numbers include all rational and irrational numbers.
Identifying complex roots of quadratic functions with the quadratic formula, and adding and subtracting complex numbers.