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If vector vecP=a hati + a hatj +3hatk a...

If vector ` vecP=a hati + a hatj +3hatk and vecQ=a hati -2 hatj -hatk ` are perpendicular to each other , then the positive value of a is

A

3

B

2

C

1

D

zero

Text Solution

Verified by Experts

The correct Answer is:
1
`vecP*vecQ= 0 rArr (ahati+ahatj+3hatk)*(ahati-2hatj-hatk)=0`
`a^(2) -2a-3=0 rArr (a-3)(a+1) =0`
`a=3 and a=-1`
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