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MHT CET202616 April 2026Morning ShiftMathematicsVector AlgebraActual

Let a = i + j , c = i - j and a vector b be such that a b = c and a b = 3 then | b | =

Options

  1. A11 2
  2. B11 3
  3. C11 2
  4. D11 3

Correct answer

C. 11 2

Step-by-step solution

Given a = i + j and c = i - j . | a |^2 = 1^2 + 1^2 = 2 | c |^2 = 1^2 + (-1)^2 = 2 Using Lagrange's identity: | a b |^2 + ( a b )^2 = | a |^2 | b |^2 Substituting the given values a b = c and a b = 3 : | c |^2 + 3^2 = | a |^2 | b |^2 2 + 9 = 2 | b |^2 11 = 2 | b |^2 | b | = 11 2 Answer: 11 2

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