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A vector coplanar with vectores ` hati + hatj and hatj + hatk ` and parallel to the vector ` 2 hati - 2 hatj - 4 hatk `isA. `hati - hatk`B. `hati - hatj -2hatk `C. `hati +hatj-hatk `D. `3hati+3hatj-6hatk` |
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Answer» Correct Answer - B Any vector coplanar with vectors ` hati + hatj and hatj + hatk ` is `a=x (hati +hatj )+y (hatj +hatk)` `implies a=xhati +(x+y)hatj +yhatk` It is given that a is paraallel to ` 2 hati - 2 hatj - 4 hatk ` ` therefore a= lamda ( 2 hati - 2hatj - 4 hatk )` for some scalar ` lamda `. `implies [ x hati +(x+y) hatj +yhatk ]= lamda (2 hati - 2hatj - 4 hatk)` `implies x= 2 lamda , x+y=- 2 lamda and y=- 4 lamda ` `implies x=2lamda and y=-4 lamda ` `therefore a= 2 lamda ( hati - hatj - 2hatk )` , where `lamda in R.` |
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