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Determinants — MATHS STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceMATHSDeterminants1 Mark
Question
Value of $k$, for which $A=\left[\begin{array}{cc}k & 8 \\ 4 & 2 k\end{array}\right]$ is a singular matrix is
✓

Answer

$\because A $ is a singular matrix.
$\therefore|A|=0 \\ \Rightarrow\left|\begin{array}{cc} k & 8 \\ 4 & 2 k \end{array}\right|
=0$ 
$\Rightarrow 2 k^2-32=0 $
$\Rightarrow k^2=16 $
$\Rightarrow k= \pm 4$
 

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