# Coordinate geometry

Let at the figure given below:

We know that the diagonals in parallelogram bisects each other. Hence, O is the midpoint of AC & BD.

So, we need to find x co-ordinate of O.

(i) Find midpoint of AC

x-coordinate of O = (x1+x2)/2

=(6+9)/2

=15/2 – (1)

(ii) Find midpoint of BD

x-coordinate of O = (x1+x2)/2

=(8+p)/2 – (2)

Equating (1) & (2),

15/2 = (8+p)/2

15 = 8 + p

p = 15-8

p = 7.