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Question: Answered & Verified by Expert
If $\left|\begin{array}{ccc}8 & -5 & 1 \\ 5 & \mathrm{x} & 1 \\ 6 & 3 & 1\end{array}\right|=2$ then what is the value of $\mathrm{x}$ ?
MathematicsDeterminantsNDANDA 2012 (Phase 1)
Options:
  • A 4
  • B 5
  • C 6
  • D 8
Solution:
1534 Upvotes Verified Answer
The correct answer is: 8
Since $\left|\begin{array}{ccc}8 & -5 & 1 \\ 5 & x & 1 \\ 6 & 3 & 1\end{array}\right|=2$
$\Rightarrow 8(x-3)+5(5-6)+1(15-6 x)=2$
$\Rightarrow 8 x-24-5+15-6 x=2$
$\Rightarrow 2 x=16$
$\Rightarrow x=8$

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