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# 4.6: Quadratic Formula and Complex Sums

Difficulty Level: At Grade Created by: CK-12
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Practice Quadratic Formula and Complex Sums

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### Vocabulary Language: English

complex number

A complex number is the sum of a real number and an imaginary number, written in the form $a + bi$.

complex root

A complex root is a complex number that, when used as an input ($x$) value of a function, results in an output ($y$) value of zero.

discriminant

The discriminant is the part of the quadratic formula under the radical, $b^2 - 4ac$. 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.

Imaginary Numbers

An imaginary number is a number that can be written as the product of a real number and $i$.

Quadratic Formula

The quadratic formula states that for any quadratic equation in the form $ax^2+bx+c=0$, $x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}$.

Real Number

A real number is a number that can be plotted on a number line. Real numbers include all rational and irrational numbers.

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Date Created:
Nov 01, 2012
Last Modified:
Mar 23, 2016
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