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3 and 4 .Determinants and Matrices
easy
જો $\left| {\,\begin{array}{*{20}{c}}5&3&{ - 1}\\{ - 7}&x&{ - 3}\\9&6&{ - 2}\end{array}\,} \right| = 0$, તો $ x$ મેળવો.
A
$3$
B
$5$
C
$7$
D
$9$
Solution
(d) We have $\Delta = \left| {\,\begin{array}{*{20}{c}}5&3&{ – 1}\\{ – 7}&x&{ – 3}\\9&6&{ – 2}\end{array}\,} \right|{\rm{ }} = {\rm{0}}$
$\therefore $ $ – 10x + 90 – 42 – 81 + 42 + 9x = 0\,\,{\rm{or}}\,{\rm{ }}x = 9$.
Std 12
Mathematics