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|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)

Guest Mar 23, 2015

Best Answer 

 #1
avatar+18829 
+5

|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)

$$\small{\text{
$
\left|
\begin{array}{rrr}
2 &-1 &2 \\
-4 &0 &1 \\
-1 &-1 &-1 \\
\end{array}
\right|
$
}}\\\\\\
\begin{array}{ll}
= &
2\cdot 0 \cdot (-1) + (-1)\cdot(-1)\cdot 1 + (-4)\cdot(-1)\cdot 2\\
&- (-1)\cdot 0 \cdot 2 - 2\cdot(-1)\cdot 1 - (-4)\cdot(-1)\cdot(-1)\\
= &
0 + 1 + 8\\
&-0 + 2 +4\\
= &
9\\
&+6\\
= 15
\end{array}
$
}}$$

see also: https://www.khanacademy.org/math/precalculus/precalc-matrices/inverting_matrices/v/finding-the-determinant-of-a-3x3-matrix-method-1

heureka  Mar 24, 2015
Sort: 

1+0 Answers

 #1
avatar+18829 
+5
Best Answer

|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)

$$\small{\text{
$
\left|
\begin{array}{rrr}
2 &-1 &2 \\
-4 &0 &1 \\
-1 &-1 &-1 \\
\end{array}
\right|
$
}}\\\\\\
\begin{array}{ll}
= &
2\cdot 0 \cdot (-1) + (-1)\cdot(-1)\cdot 1 + (-4)\cdot(-1)\cdot 2\\
&- (-1)\cdot 0 \cdot 2 - 2\cdot(-1)\cdot 1 - (-4)\cdot(-1)\cdot(-1)\\
= &
0 + 1 + 8\\
&-0 + 2 +4\\
= &
9\\
&+6\\
= 15
\end{array}
$
}}$$

see also: https://www.khanacademy.org/math/precalculus/precalc-matrices/inverting_matrices/v/finding-the-determinant-of-a-3x3-matrix-method-1

heureka  Mar 24, 2015

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