Find the equation of the plane passing through the point A(2, 1, 3), B(-1, 2, 4) and C(0, 2, 1). Also determine its point of intersection with the line r=i−j+k+t(2i+k).
A
(7,−1,4).
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B
(7,1,4).
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C
(7,−1,−4).
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D
(−7,1,−4).
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Solution
The correct option is A(7,−1,4). If n be the normal of the plane ABC, then n=→AB×→AC=−3i−8j−k Plane is (r−a)⋅n=0⇒r⋅n=a⋅n ⇒r⋅(3i+8j+k)=17 ...(1) The given line is r=(1+2t)i+(−1)j+(1+t)k=0 ...(2) For point of intersection we have from (1) and (2) 3(1+2t)−8+(1+t)=17∴7t=21 or t = 3 Substitute for t in (2) the point of intersection is given by r=7i−j+4k. ∴ Its co-ordinates are (7,−1,4).