The three lines drawn from O with direction ratios, (1, –1, k), (2, –3, 0) and (1, 0, 3) are coplanar. Then k =
A
1
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B
no such k exists
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C
7
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Solution
The correct option is A 1 If lines are coplanar and l, m, n are d.c.’s of the normal to the plane, then l – 1.m + k.n = 0 l – 3.m + 0.n = 0 l – 0.m + 3.n = 0 ⇒∣∣
∣∣1−1k2−30103∣∣
∣∣=0⇒k=1