Question 1139121:  Show in two ways that the quadrilateral with vertices (0, -1) (1, 2) (-4, 7) and (-5, 4) is a parallelogram. 
 Answer by Alan3354(69443)      (Show Source): 
You can  put this solution on YOUR website! Show in two ways that the quadrilateral with vertices (0, -1) (1, 2) (-4, 7) and (-5, 4) is a parallelogram. 
------- 
Label the points A(0,-1), B(1,2), C(-4,7) and D(-5,4) 
--- 
The points are in order around the figure. 
--- 
Method 1: 
If the lengths of AB and CD are equal, and BC and AD are equal, it's a p-gram. 
==================== 
Method 2: 
If AB is parallel to CD and BC is parallel to AD, it's a p-gram. 
 
  | 
 
  
 
 |   
 
 |