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AP EAMCET202125 Aug 2021Morning ShiftMathematicsStraight LinesActual

If the straight lines 2 x-y+1=0 , 4 x+y+2=0 and x+y-k=0 are concurrent, then k equals

Options

  1. A1 2
  2. B2
  3. C-2
  4. D-1 2

Correct answer

D. -1 2

Step-by-step solution

Given lines, array r 2 x-y+1=0 4 x+y+2=0 x+y-k=0 array are concurrent. aligned & & & | array rrc 2 & -1 & 1 4 & 1 & 2 1 & 1 & -k array |=0 & & 2(-k-2)+1(-4 k-2)+1(4-1) & =0 & & -2 k-4-4 k-2+3 & =0 & & -6 k & =3 & & k & =-1 / 2 aligned

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