1.

If for a unit vector a.(x-a).(x+a)=12, then |x| is equal to

Answer»

4
2
`sqrt(13)`
`sqrt(11)`

Solution :Given |a|=1
[` :'`Itis a unitvector, mangnitude of unitvector is 1 ]
` therefore(x-a).(x+a)=12`
`IMPLIES x.x+x.a-a.x-a.a=12`
`[ :'a.a =|a|^(2) anda.b=b.a]`
`implies |x|^(2)-|a|^(2) = 12implies |x|^(2) -1^(2)=12`
`[ :'|a|=1 ` asit is unitvector ]
` | x|^(2)= 13gt |x|= sqrt(13)`


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