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Real Numbers Squares Sum

Let $ a, $ $ b, $ $ c, $ and $ d $ be real numbers such that $ a^2 + b^2 = 8 $ and $ c^2 + d^2 = 13 $. Find \[(ad - bc)^2 + (ac + bd)^2.\]

1
2
3
+
4
5
6
-
7
8
9
$\frac{a}{b}$
.
0
=
%

$a^n$
$a^{\circ}$
$a_n$
$\sqrt{}$
$\sqrt[n]{}$
$\pi$
$\ln{}$
$\log$
$\theta$
$\sin{}$
$\cos{}$
$\tan{}$

$($
$)$
$[$
$]$
$\cap$
$\cup$
$,$
$\infty$