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AP EAMCET2007MathematicsDeterminants

If [ array rrr 1 & 2 & x 4 & -1 & 7 2 & 4 & -6 array ] is a singular matrix, then x is equal to

Options

  1. A0
  2. B1
  3. C-3
  4. D3

Correct answer

C. -3

Step-by-step solution

Let A= [ array ccc 1 & 2 & x 4 & -1 & 7 2 & 4 & -6 array ] is a singular matrix Then, |A|=0 aligned & | array ccc 1 & 2 & x 4 & -1 & 7 2 & 4 & -6 array |=0 & 1[6-28]-2[-24-14]+x[16+2]=0 & -22-2 (-38)+x 18=0 & -22+76+18 x=0 & x=-3 & aligned

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