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Model Paper 8 — MATHS STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceMATHSModel Paper 81 Mark
Question
For which value of $x$, are the determinants $\left|\begin{array}{cc}2 x & -3 \\ 5 & x \end{array}\right|$ and $\left|\begin{array}{rr}10 & 1 \\ -3 & 2\end{array}\right|$ equal?
✓

Answer

$(c) \pm 2$
Explanation:  $\pm 2$
$\left|\begin{array}{cc}2 x & -3 \\ 5 & x \end{array}\right|=\left|\begin{array}{rr}10 & 1 \\ -3 & 2\end{array}\right|$
$2 x^2+15=20+3$
$2 x^2=23-15$
$2 x^2=8$
$x^2=4$
$x= \pm 2$

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