第11章 11.6

(1)

$2 + 3i$

$|2 + 3i| = \sqrt{4 + 9} = \sqrt{13}$

(2)

$1 - 4i$

$|1 - 4i| = \sqrt{1 + 16} = \sqrt{17}$

(3)

$-\sqrt{2} + i$

$|-\sqrt{2} + i| = \sqrt{2 + 1} = \sqrt{3}$

(4)

$-3i$

$|-3i| = 3$