<PRE><B>Question 260453</B>
Given: A (4,3), B (8,3), C (9,10), and D (5,10) are vertices of a quadrilateral.  Is quadrilateral ABCD a parallelogram?  Use mathmatics to justify your answer.  (graphing is not acceptable)
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Plot the points so you can see what is happening.
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Is ABCD a parallelogram?
Check the slopes of opposite sides.
ABslope: (3-3)/(8-4)= 0
CDslope: (10-10)/(5-9) = 0
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BCslope: (10-3)/(9-8) = 7/1 
ADslope: 7/1
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Opposite sides are parallel so it is a parallelogram.
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Cheers,
Stan H.</PRE>