Question

For what value of x , will the two vector `A= 2hati + 2hatj -x hatk and B =2 hati - hatj - 3hatk ` are perpendicular to each other ?
A. `x=-2//3`
B. `x=-3//2`
C. `x=-4//3`
D. `x=-2//3`

Answer 1

Correct Answer - A
(a) For vector to be perpendicular ,
`A.B=0`
`implies(2hati+2hatj-xhatk).(2hati-hatj-3hatk)=0`
`implies4-2+3x=0`
`implies3x=- or x=(-2)/(3)`