Answer with explanation:
Quadrilateral has four sides.The Different types of Quadrilateral are:
 1. Parallelogram----Opposite sides are Parallel.
 2. Rhombus--Opposite sides are Parallel.
 3. Square----Opposite sides are Parallel and adjacent sides are perpendicular.
 4.Rectangle----Opposite sides are Parallel and adjacent sides are perpendicular.
 5.Kite...............................
So, Slope formula is used to determine 
Quadrilateral has either parallel or perpendicular sides.