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8·The vector P=ai + aj + 3k and Q = ai-2-kareperpendicular to each other. The positive value ofa is:EAMCET 1998, AIIMS 2002](2) 2(4) zero(3) 1 |
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Answer» If two vectors are perpendicular , their dot product will be Zero. It's a condition P= ai + aj+3k Q=ai -2j-k P.Q= (ai+aj+3k).(ai-2j-k)=0 mulitply their equal components a^2 -2a -3 =0 Factorisation of a^2-2a -3 is (a+1)(a-3)So, a+1=0. a-3=0 a=-1. a=3In positive value ,Here positive value is 3 So the answer is 3 |
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