Find the ratio in which the line segment joining the points (4, 8, 10) and (6, 10, –8) is divided by the yz-plane.
Let A = (4, 8, 10) , B = (6, 10, 8)
Let the line joining A and B be divided by the YZ-plane at point P in the ratio .
Since P lies on the YZ-plane, the x-coordinate of P will be zero.
Hence, the YZ-plane divides AB in the ratio 2:3 (externally)
RD Sharma XI (2015)