1.

If (l_(1),m_(1),n_(1)),(l_(2),m_(2),n_(2)) are d.c's of two lines then find the value of (l_(1)m_(2)-l_(2)m_(1))^(2)+(m_(1)n_(2)-n_(1)m_(2))^(2)+(n_(1)l_(2)-n_(2)l_(1))^(2)+(l_(1)l_(2)+m_(1)m_(2)+n_(1)n_(2))^(2)

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3
2
1
4

Answer :C


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