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JEE Main2011MathematicsVector AlgebraActual

If a = 1 10 (3 i + k ) and b = 1 7 (2 i +3 j -6 k ) , then the value of (2 a - b ) [( a b ) ( a +2 b )] is

Options

  1. A-3
  2. B5
  3. C3
  4. D-5

Correct answer

D. -5

Step-by-step solution

(2 a - b ) ( a b ) ( a +2 b ) =(2 a - b ) [ a ( a +2 b )] b -[ b ( a +2 b ) a ] =-5( a )^2( b )^2+5( a b )^2=-5

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