Vectors question - given points

[Random-Hero-]

Vectors question -- given points

Lads, You're going to laugh at me, but I started my new unit today, and I forgot my dang textbook at school, I'm doing as much research online as I can, but I'm having a rough time figuring this guy out. Any insight would be very helpful! Thanks!

Homework Statement

Given the points A(-3,1), B(4,7), C(9,2), and D(2,-4) prove algebraically that they form a parallelogram.

 

[Mark44]

If these points form a parallelogram, opposite sides must be parallel and equal in length. Form vectors of AB, DC, AD, and BC. The first two vectors I've listed should be equal (and therefore parallel). So should the last two.