Answer
$ad-bc=6$
Work Step by Step
Substituting $
a=-1
,$ $
b=-2
,$ $
c=5
,$ $
d=4
$ in the expression $ad-bc,$ then
\begin{align*}\require{cancel}
&
\left( -1 \right)\left( 4 \right)-\left( -2 \right)\left( 5 \right)
\\&=
-4-\left( -10 \right)
\\&=
-4+10
\\&=
6
.\end{align*}
Hence, $
ad-bc=6
$.
