Definition:Root of Number

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Definition

Let $x, y \in \R_{\ge 0}$ be positive real numbers.

Let $n \in \Z$ be an integer such that $n \ne 0$.


Then $y$ is the positive $n$th root of $x$ if and only if:

$y^n = x$

and we write:

$y = \sqrt[n] x$


Using the power notation, this can also be written:

$y = x^{1/n}$


When $n = 2$, we write $y = \sqrt x$ and call $y$ the positive square root of $x$.

When $n = 3$, we write $y = \sqrt [3] x$ and call $y$ the cube root of $x$.


Note the special case where $x = 0 = y$:

$0 = \sqrt [n] 0$


Index

Let $\sqrt [n] x$ denote the $n$th root of $x$.

The number $n$ is known as the index of the root.


If $n$ is not specified, that is $\sqrt x$ is presented, this means the square root.


Extraction of Root

The process of evaluating roots of a given real number is referred to as extraction.


Examples

$4$th Roots of $16$

The set of $4$th roots of $16$ is:

$\set {2, -2, 2 i, -2 i}$


Also known as

A root of a number is also known as:

a radical
a radix.


Also see

  • Results about roots of numbers can be found here.


Sources

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