| , * 20 c 5&3& - 1 - 7 &x& - 3 9&6& - 2 , | = 0, then x is equal… - Vidyadip

MCQ

$\left| {\,\begin{array}{*{20}{c}}5&3&{ - 1}\\{ - 7}&x&{ - 3}\\9&6&{ - 2}\end{array}\,} \right| = 0$, then $ x$ is equal to

A
$3$
B
$5$
C
$7$
✓
$9$

✓

Answer

Correct option: D.

$9$

d
(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$.

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