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NEET Sample Paper NEET Sample Test Paper-26

  • question_answer
    Vectors \[A=ai+aj+3k\] and \[B=ai-2j-k\] are perpendicular to each other, then the positive value of a is:

    A)  3                 

    B)  2

    C)  1                    

    D)  0

    Correct Answer: A

    Solution :

    If \[A\bot B,\]  then    \[A.B=0\] \[{{a}^{2}}-2a-3=0\] \[\Rightarrow \]                \[(a+1)\,(a-3)=0\] \[\Rightarrow \]               \[a=-1\] or  \[=3\] [Since magnitude cannot be (negative)]


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