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MHT CET202312 May 2023Morning ShiftMathematicsVector AlgebraActual

If a , b , c are three vectors, | a |=2,| b |=4,| c |=1 , | b c |= 15 and b =2 c + a , then the value of , is

Options

  1. A2
  2. B2 2
  3. C1
  4. D4

Correct answer

D. 4

Step-by-step solution

If angle between b and c is and aligned & | b c |= 15 & | b || c | = 15 & = 15 4 & = 1 4 aligned Now, b -2 c = a aligned & | b -2 c |^2= ^2| b |^2 & | b |^2+4| c |^2-4 b c = . . ^2 |^ - a |^2 & 16+4-4 | b || c | = ^2 & 16+4-4 4 1 1 4 = ^2 & ^2=16 & = 4 aligned

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