Given: points A(2, 4, 5) and B(3, 5, -9)

To find: the ratio in which the line joining given points is divided by the yz-plane

Formula used:

Section Formula:

A line AB is divided by C in m:n where A(x, y, z) and B(a, b, c).

The coordinates of C is given by,

x coordinate is always 0 on yz-plane

Let Point C(0, y, z) and C divides AB in ratio k : 1

Therefore, m = k and n = 1

A(2, 4, 5) and B(3, 5, -9)

Coordinates of C using section formula:

On comparing:

⇒ 3k + 2 = 0(k + 1)

⇒ 3k + 2 = 0

⇒ 3k = –2

Hence, C divides AB externally in ratio 2 : 3