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Evaluate : $ 2\begin{vmatrix} 7 & -2 \\ -10 & 5 \end{vmatrix} $

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  • $\begin{vmatrix}a_{11} & a_{12}\\a_{21} & a_{22}\end{vmatrix}=a_{11}\times a_{22}-a_{12}\times a_{21}$
Let $\Delta=\begin{vmatrix}7 &-2\\-10 & 5\end{vmatrix}$
On expanding we get,
$\Delta=7\times 5-(-10\times -2)$
$\quad=35-20$
$\quad=15$
$2\begin{vmatrix}7 &-2\\-10 & 5\end{vmatrix}=2\times 15=30$
answered Mar 28, 2013 by sreemathi.v
 
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