# How do you find abs( 7+9i )?

May 6, 2016

$| 7 + 9 i | = \sqrt{130}$

#### Explanation:

Given a complex number $a + b i$, the modulus of that number, denoted $| a + b i |$, is the distance from that number to the origin on the complex plane. Then, we have

$| a + b i | = \sqrt{{a}^{2} + {b}^{2}}$.

In this case, that gives us

$| 7 + 9 i | = \sqrt{{7}^{2} + {9}^{2}} = \sqrt{130}$