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The position vectors of P and Q are 5hat...

The position vectors of P and Q are `5hati+4hatj+ahatk` and `-hati+2hatj-2hatk`, respectively. If the distance betwee them is 7, then the value of a will be

A

`-5,1`

B

`5,1`

C

`0,5`

D

1,0

Text Solution

Verified by Experts

The correct Answer is:
A
`7=sqrt((5+1)^(2)+(4-2)^(2)+(a+2)^(2))`
`implies a+2=+-3impliesa=-5,1`
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