Q9 of 45 Page 1

The x-coordiante of a point on the line joining the points

P(2, 2, 1) and Q(5,1,-2) is 4. Find its z-coordiante.

Let (x1, y1, z1) ≡ (2, 2, 1)

(x2, y2, z2) ≡ (5, 1, -2)


The equation of a line passing through points (x1, y1, z1) and


(x2, y2, z2) is given by-



Thus, the equation of line PQ is-




taking 1st and 3rd part of equality,



⇒ x - 2 = -(z - 1)


⇒ x - 2 = -z + 1


⇒ z = -x + 3


Putting x = 4, we will get the z-coordinate of the point


z = -4 + 3 = -1


Thus, the z-coordinate of the point lying on the line PQ whose x-coordinate is 4 is -1.


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