to find this out you need to know (x,y) and y-y/x-x
so the two y's are 0 and 4 so its 0-4
then the two x's are 0 and one so its 0-1
0-4/0-1 is -4/-1 which when simplified the negatives cancel out leaving you with a positive 4 I hope this helps you, also you should use m a t h w a y its perfect for learning this unit and many more :)
