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MHT CET2012MathematicsVector Algebra

If three vectors 2 i - j - k , i +2 j -3 k and 3 i + j +5 k are coplanar, then the value of is

Options

  1. A-4
  2. B-2
  3. C-1
  4. D-8

Correct answer

D. -8

Step-by-step solution

Let a =2 i - j - k , b = i +2 j -3 k and c =3 i + j +5 k If these vectors are coplanar, then [ a b c ]=0 array l | array ccc 2 & -1 & -1 1 & 2 & -3 3 & & 5 array |=0 2(10+3 )+(5+9)-( -6)=0 20+6 +14- +6=0 5 +40=0 =-8 array

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