|2 -1 2|
|-4 0 1|
|-1 -1 -1|
(the vertical line at the front and back of each one are all suppose to be connected vertically)
|2 -1 2|
|-4 0 1|
|-1 -1 -1|
(the vertical line at the front and back of each one are all suppose to be connected vertically)
$$\small{\text{
$
\left|
\begin{array}{rrr}
2 &-1 &2 \\
-4 &0 &1 \\
-1 &-1 &-1 \\
\end{array}
\right|
$
}}\\\\\\
\begin{array}{ll}
= &
2\cdot 0 \cdot (-1) + (-1)\cdot(-1)\cdot 1 + (-4)\cdot(-1)\cdot 2\\
&- (-1)\cdot 0 \cdot 2 - 2\cdot(-1)\cdot 1 - (-4)\cdot(-1)\cdot(-1)\\
= &
0 + 1 + 8\\
&-0 + 2 +4\\
= &
9\\
&+6\\
= 15
\end{array}
$
}}$$
|2 -1 2|
|-4 0 1|
|-1 -1 -1|
(the vertical line at the front and back of each one are all suppose to be connected vertically)
$$\small{\text{
$
\left|
\begin{array}{rrr}
2 &-1 &2 \\
-4 &0 &1 \\
-1 &-1 &-1 \\
\end{array}
\right|
$
}}\\\\\\
\begin{array}{ll}
= &
2\cdot 0 \cdot (-1) + (-1)\cdot(-1)\cdot 1 + (-4)\cdot(-1)\cdot 2\\
&- (-1)\cdot 0 \cdot 2 - 2\cdot(-1)\cdot 1 - (-4)\cdot(-1)\cdot(-1)\\
= &
0 + 1 + 8\\
&-0 + 2 +4\\
= &
9\\
&+6\\
= 15
\end{array}
$
}}$$