# How do you find abs( -4-9i )?

$| - 4 - 9 i \lceiling = 9.85 .$
For a complex no. $z = x + i y ,$ $| z | = | x + i y | = \sqrt{{x}^{2} + {y}^{2}} .$
Hence, $| - 4 - 9 i | = \sqrt{16 + 81} = \sqrt{97} \cong 9.85 .$