1.

Let a=hatj-hatk and c=hati-hatj-hatk, the vector b satisfying axxb+c=vec0 and a.b=3, is

Answer»

`-hati+hatj-2hatk`
`2hati-hatj+2hatk`
`hati-hatj-2hatk`
`hati+hatj-2hati`

Solution :Given , `a xx B+ c = 0`
`RARR a xx (a xx b) + a xx c = 0`
`rArr (a.b)a - (a.a) + a xx c = 0`
`rArr 3a - 2B +a xx c = 0`
`rArr 2b =3a+a xx c`
`rArr 2b = 3hatj - 3hatk -2hati - hatj - hatk`
`rArr 2b = - hati + 2hatj - 4hatk`
`:. b= - hati + hatj - 2hatk`


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