The mirror image of the point  1,2,3in a plane is−73,−43,−13 . Which of the following lies on this plane?

The direction ratios of normal to the plane are /103,103,103 ) same as ⟨1,1,1⟩ Midpoint of the line segment joining the points (1,2,3) and -73,-43,-13 is -23,13,43Therefore, the Equation of plane is x + y + z = 1