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Find length of sides of quadrilateral; write equation

  1. Oct 14, 2012 #1
    1. The problem statement, all variables and given/known data

    I have a seemingly simple question. I have a quadrilateral with sides (starting with the left side, moving clockwise):(7-x), (x+2), (2x-1), (x-3).

    a) write an equation for the perimeter and simplify: that's easy, and done. This ends up as 3x+5

    b) Find the length of all sides. Using the result from above, 3x+5 = -5/3, and would give one of the sides a -negative answer. I assume one cannot have a negative length?


    2. Relevant equations

    P = (7-x)+(x+2)+(2x-1)+(x-3)
    =3x+5

    x = -5/3?

    3. The attempt at a solution

    If x=-5/3, then;
    P=(7-5/3)+(5/3+2)+(2x5/3-1)+(5/3-3)
    =5 1/3 + 3 2/3 + 21/3 + -1 1/3
     
  2. jcsd
  3. Oct 14, 2012 #2

    LCKurtz

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    That isn't an equation of anything. Nothing you have written so far is an equation because equations have an = sign and two sides.

    I can't make sense of any of that. You need to find where the sides intersect (the vertices) and use the distance formula to calculate the perimeter.
     
  4. Oct 15, 2012 #3
    Hi,

    thanks for taking the time to respond.

    I have spent a couple of days looking at this problem and have just discovered that a vital bit of information was there the whole time: the perimeter is 23cm!

    Problem solved.

    Thanks
     
  5. Oct 15, 2012 #4

    LCKurtz

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    Really?? That's pretty amazing. Given that the expressions above all should have "y =" on their left sides, those lines don't even form a quadrilateral.
     
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