Question

9. If the points A(6, 1), B (8, 2), C (9, 4) and D (x 3) are the vertices of a parallelogram,
taken in order then the value of x is
[ ]
a) 7
b) 5
c) 4
d) None​

Answer 1

We know that the diagonals of a parallelogram bisect each other. So, coordinates of the mid-point of diagonal AC are same as the coordinates of the mid-point of diagonal BD.

=>(6+9/2,1+4/2)=(8+x/2,2+3/2).

=>(15/2,5/2)=(8+x/2,5/2)

=>15/2=8+x/2

=>15=8+x

=>x=7

Therefore, option A is correct.