Parallelograms

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bookworm396

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Jan 22, 2008
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Find the values of x and y that ensure each quadrilateral is a parallelogram.

3x+17 parallels 2y

4 parallels 4x-y



I couldn't figure out how to put a parallelogram :?: in, so I hope my directions are clear. If not, post and let me know so I can clarify.
 
The opposite sides of a parallelogram are parallel and equal in length. Therefore just change your words "parallels" to = and solve the two resulting equations simultaneously.
 
bookworm396 said:
I tried that but I came up with a really strange answer...
Click to expand...

Please show your work - and that strange answer - so that we know where to begin to help you.
 
4=4x-y
1=x-y
y+1=x

3x+17=2y
3x=0.117647059y
25.5x=y

I don't know if I did that right or not, and if I did, I don't know what to do next.
 
bookworm396 said:
4=4x-y
1=x-y<<<<<<<<<<<<<< How is that? Only 'x' has a coefficient of '4' - not 'y'
y+1=x

3x+17=2y
3x=0.117647059y<<<<<<<<<<<<<< How is that?
25.5x=y

I don't know if I did that right or not, and if I did, I don't know what to do next.
Click to expand...

You have two equations and two unknows.

4x - y = 4....................................................(1)

3x - 2y = -17...............................................(2)

You need to solve those simutaneously. For a quick refresher, go to,

http://www.purplemath.com/modules/systlin1.htm

You could do this by "method of substitution"

From (1)

y = 4x - 4 ...........................................................(3)

Use (3) in (2) to get

3x - 2(4x-4) = 17.................................................(4)

Solve for 'x' from (4). Then use that value of 'x' in (3) to solve for 'y'.

Finally, check your answer by using these values of 'x & 'y' in (1) and (2) - to see if thosee satisfy the equations.
 
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