SOLUTION: If point A(6,1),B (8,2),C (8,4),D (p,3) are vertices of a parallelogram taken in order, find value of p

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Question 1070634: If point A(6,1),B (8,2),C (8,4),D (p,3) are vertices of a parallelogram taken in order, find value of p
Found 2 solutions by stanbon, MathTherapy:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
If point A(6,1),B (8,2),C (8,4),D (p,3) are vertices of a parallelogram taken in order, find value of p
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Plot the 3 given points so you can see where the 4th
point would have to be.
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AC is parallel to BD
AC has a slope of (4-1)/(8-6) = 3/2
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So BD must have a slope of 3/2
slope of BD :: (3-2)/(p-8) = 3/2
1/(p-8) = 3/2
3p-24 = 2
3p = 26
p = 8 2/3
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Cheers,
Stan H.
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Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!
If point A(6,1),B (8,2),C (8,4),D (p,3) are vertices of a parallelogram taken in order, find value of p
AB ∥ DC and BC ∥ AD
BC is a VERTICAL line that's parallel to the y-axis, and parallel and congruent to AD. BC's length = 4 - 2, or 2
AD is a VERTICAL line that's parallel to the y-axis, and parallel and congruent to BC. Points A and D will therefore have the SAME x-coordinate, which is 6.
Therefore, p = 6.

OR

You can also see that AB and DC are parallel, and so, have the same slope. Slope of AB = matrix%281%2C5%2C+%281+-+2%29%2F%286+-+8%29%2C+or%2C+%28-+1%29%2F%28-+2%29%2C+or%2C+1%2F2%29
DC's slope also = 1%2F2. 
To find p, we get: