# How do you find abs( -3 + 7i )?

$| - 3 + 7 i | = \sqrt{58}$
Absolute value of a complex number $a + b i$ is written as $| a + b i |$ and is equal to $\sqrt{{a}^{2} + {b}^{2}}$
Hence absolute value of $- 3 + 7 i$ is
$| - 3 + 7 i | = \sqrt{{\left(- 3\right)}^{2} + {7}^{2}} = \sqrt{9 + 49} = \sqrt{58}$