nth root
An n-th root of a number r is a number which, if n copies are multiplied together, makes r. It is also called a radical or a radical expression. It is a number k for which the following equation is true:
- [math]\displaystyle{ k^n=r }[/math]
(for the meaning of [math]\displaystyle{ k^n }[/math], see Exponentiation.)
We write the nth root of r as [math]\displaystyle{ \sqrt[n]{r} }[/math].[1] If n is 2, then the radical expression is a square root. If it is 3, it is a cube root.[2][3] Other values of n are referred to using ordinal numbers, such as fourth root and tenth root.
For example, [math]\displaystyle{ \sqrt[3]{8} = 2 }[/math] because [math]\displaystyle{ 2^3 = 8 }[/math]. The 8 in that example is called the radicand, the 3 is called the index, and the check-shaped part is called the radical symbol or radical sign.
Roots and powers can be changed as shown in [math]\displaystyle{ \sqrt[b]{x^a} = x^\frac{a}{b} = (\sqrt[b]{x})^a = (x^a)^\frac{1}{b} }[/math].
The product property of a radical expression is the statement that [math]\displaystyle{ \sqrt{ab} = \sqrt{a} \times \sqrt{b} }[/math]. The quotient property of a radical expression is the statement [math]\displaystyle{ \sqrt{\tfrac{a}{b}} = \tfrac{\sqrt{a}}{\sqrt{b}} }[/math].[3], b != 0.
Simplifying
This is an example of how to simplify a radical.
- [math]\displaystyle{ \sqrt{8} = \sqrt{4 \times 2} = \sqrt{4} \times \sqrt{2} = 2\sqrt{2} }[/math]
If two radicals are the same, they can be combined. This is when both of the indexes and radicands are the same.[4]
- [math]\displaystyle{ 2\sqrt{2} + 1\sqrt{2} = 3\sqrt{2} }[/math]
- [math]\displaystyle{ 2\sqrt[3]{7} - 6\sqrt[3]{7} = -4\sqrt[3]{7} }[/math]
This is how to find the perfect square and rationalize the denominator.
- [math]\displaystyle{ \frac{8x}{\sqrt{x}^3} = \frac{8\cancel{x}}{\cancel{x}\sqrt{x}} = \frac{8}{\sqrt{x}} = \frac{8}{\sqrt{x}} \times \frac{\sqrt{x}}{\sqrt{x}} = \frac{8\sqrt{x}}{\sqrt{x}^2} = \frac{8\sqrt{x}}{x} }[/math]
Nth Root Media
Pascal's triangle showing P(4,1) = 4.
Related pages
References
- ↑ "List of Arithmetic and Common Math Symbols". Math Vault. 2020-03-17. Retrieved 2020-09-22.
- ↑ Weisstein, Eric W. "nth Root". mathworld.wolfram.com. Retrieved 2020-09-22.
- ↑ 3.0 3.1 "nth Roots". www.mathsisfun.com. Retrieved 2020-09-22.
- ↑ "Add and Subtract Radicals". mathbitsnotebook.com. Retrieved March 14, 2018.