Question 1127887:  [Quadrilateral] If the oppisite sides of a quadrilateral are use parallel, then it is a parallelogram. Use slopes to determine wheather the points (-6,1),(-2,-1),(0,3), and (4,1) are the vertices of a parallelogram. 
 Found 2 solutions by  josmiceli, MathLover1: Answer by josmiceli(19441)      (Show Source): 
You can  put this solution on YOUR website! A( -6,1 ) 
B( -2,-1 ) 
C( 0,3 ) 
D( 4,1 ) 
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slope AB = ( 1 -(-1) ) / ( -6 -(-2) ) 
slope AB = 2/(-4)  
slope AB = -1/2 
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slope BC = ( 3 -(-1) ) / ( 0 -(-2) ) 
slope BC = 4/2 
slope BC = 2 
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slope AC = ( 3 - 1 ) / ( 0 -(-6) 
slope AC = 2/6  
slope AC = 1/3 
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slope BD = ( 1 -(-1) ) / ( 4 -(-2) ) 
slope BD = 2/6  
slope BD = 1/3 
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slope AD = ( 1 - 1 ) / ( 4 -(-6) 
slope AD = 0 
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slope CD = ( 1 - 3 ) / ( 4 - 0 ) 
slope CD = -2 / 4  
slope CD = -1/2 
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There are 1 pair of parallel lines with slope = -1/2 
Also, there are 1 pair of parallel lines with slope = 1/3 
So it is a parallelogram, and the lines BC and AD 
must be the diagonals
 
 
 
 
 
 
 Answer by MathLover1(20850)      (Show Source): 
You can  put this solution on YOUR website! 
 
( , ),( , ),( , ), and ( , )
 
( , ),( , )->the oppisite sides of a quadrilateral are use parallel
 
  
  
  
 
 
(0,3), (4,1) 
  
  
 
 
since slopes are same, lines passing through points above are parallel
 
 
( , ),( , ) other the oppisite sides of a quadrilateral are use parallel
 
  
  
 
 
(-2,-1),(4,1) 
  
  
  
 
 
since slopes are same, lines passing through points above are parallel 
 
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