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Question: Answered & Verified by Expert
The plane passing through the point (4, -1, 2) and parallel to the lines x+23=y-2-1=z+12 and x-21=y-32=z-43 also passes through the point
MathematicsThree Dimensional GeometryJEE MainJEE Main 2019 (10 Jan Shift 1)
Options:
  • A 1, 1, -1
  • B -1, - 1, -1
  • C -1, -1, 1
  • D 1, 1, 1
Solution:
1970 Upvotes Verified Answer
The correct answer is: 1, 1, 1

Let n be the normal vector to the plane passing through (4, -1, 2) and parallel to the given lines, then we know that n is perpendicular to both the lines.

Also, we know that a vector perpendicular to two vectors lie along the cross product of the two vectors.

Hence, n=i^j^k^3-12123 

n=-7i^-7j^+7k^

Thus, the direction ratios of the normal to the plane are <-7, -7, 7>.

The equation of a plane having direction ratios of the normal to the plane as a, b, c and passing through a point x1, y1, z1 is ax-x1+by-y1+cz-z1=0

Hence, the equation of the plane having direction ratios the normal to the plane as <-7, -7, 7> and passing through the point4, -1, 2 is 

-7x-4-7y+1+7z-2=0

-7x-7y+7z=-7

x+y-z=1

From the given options only the point 1, 1, 1 satisfy the equation of the plane.

Hence, the plane passes through the point 1, 1, 1.

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