Hello, rcfreak339!
I don't suppose you made a sketch . . .
Code:
 D
 o
 :
 : C
 : o (8,7)
 : :
(2,1)  : :
A o     * :9
     +        :   
 :
 B o     *
 (2,2) 6

Since lists the vertices in order,
. . the diagram shows the position of vertex
Going from to , we move right 6, up 9.
Since is parallel to , we must do the same from vertex
Moving "right 6, up 9" from puts us at: .
(b) Determine if parallelogram is a rectangle. Compare the slopes of and
. .
. .
The slopes are not negative reciprocals of each other.
Hence, is not perpendicular to
Therefore, is not a rectangle.