Question

A school is preparing the stage for its annual day function. They want to place a hanging mic and a hanging light on the stage. • They decide to position the mic at the point (3,2,1) such that it is equidistant from a plain backdrop and the hanging light as shown below. • The equation of the surface of the plain backdrop is 2x - y + z + 1 = 0

The distance of the point 2i + j − k from the plane r·(i − 2j + 4k) = 9 will be: