1.

If the position vectors off A,B,C and D are `2hati+hatj,hati-3hatj,3hati+2hatj and hati+lamdahatj`, respectively and `AB||CD`, then `lamda` will beA. `-7`B. 7C. `-6`D. None of these

Answer» Correct Answer - C
Now, `PQ= (hati - 3 hatj)-(2 hati + hatj) = - hati-4hatj`
`and RS= - 2hati + (mu - 2)hatj`
Given, `PQ||RS rArr PQ= lambda RS`
`-hati - 4 hatj =[ lambda { - 2hati +(mu-2)hatj}]`
`rArr lambda = 1//2 and mu = -6 `


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