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Question:

The length of the perpendicular drawn from the point (2,1,4) to the plane containing the lines r→=(i^+j^)+λ(i^+2j^-k^) and r→=(i^+j^)+μ(-i^+j^-2k^) is

3

3

13

13

Solution:

Correct option is A. 3
Perpendicular vector to the plane
n→=|ijk12-1-11-2|=−3i^+3j^+3k
Eq. of plane -3(x-1)+3(y-1)+3z=0 => x-y-z=0
d(2,1,4)=|2-1-4|/√1²+1²+1²=3.