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JEE Main & Advanced Mathematics Vector Algebra Question Bank Modulus of vector Algebra of vectors

  • question_answer
    If \[\mathbf{a}=(1,\,\,-1)\] and \[\mathbf{b}=(-\,2,\,m)\] are two collinear vectors, then m=                                                     [MP PET 1998]

    A) 4             

    B) 3

    C) 2

    D) 0

    Correct Answer: C

    Solution :

    Condition for collinearity, \[\mathbf{b}=\lambda \mathbf{a}\] \[\Rightarrow (-2\mathbf{i}+m\mathbf{j})=\lambda (\mathbf{i}-\mathbf{j})\] Comparison of coefficient, we get \[\Rightarrow \lambda =-2\] and \[-\lambda =m.\] So, \[m=2\].               


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