Q227 / 270 · NDA 2012 (Phase 1) · Mathematics

If $\left|\begin{array}{ccc}8 & -5 & 1 \\ 5 & x & 1 \\ 6 & 3 & 1\end{array}\right|=2$, then what is the value of $x ?$

  • A
    4
  • B
    5
  • C
    6
  • Correct answer
    D
    8

Solution

$\begin{aligned} & 8(x-3)+5(5-6)+1(15-6 x)=2 \\ & 8 x-24-5+15-6 x=2 \\ & 2 x-14=2 \\ & 2 x=16 \Rightarrow x=8\end{aligned}$

Hence, the correct answer is option: 'D'.

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