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Quadratic help

  1. Mar 14, 2006 #1
    hi everyone! I am new to this site and hope you can help me out a little :)

    This is a homework question but am unsure how to do these types of equations

    y = - x + 5
    y = x² - 16 x + 59

    x= and y= or x= and y=

    could someone tell me how you go about doing these equations?

    Thanks
     
  2. jcsd
  3. Mar 14, 2006 #2

    Integral

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    The general method for this type of problem is to isolate one variable, then use the resulting equation in the second equation to solve for the single remaining variable.

    Give it a try and show us what you are doing.
     
  4. Mar 18, 2006 #3
    another approach, given "easy" equations is to draw the equations on X,Y plane and see how many intersections you get. the number of intersection is the number of (x,y) answers you'll get.
    i.e. if you're drawing shows no intersections this means you got no answer...
     
  5. Mar 18, 2006 #4

    Hootenanny

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    Yeah a rough sketch will show how many solutions you will have. As for solving equations graphically, that's something I hate :yuck: . As intergral said, you would usually isolate one variable, then solve for that variable. Start by trying to make one equation from the two you are given.
     
  6. Mar 18, 2006 #5

    HallsofIvy

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    Since y= both -x+ 5 and x2- 16x+ 59, them must be equal to each other: x2- 16x+ 59= -x+ 5. Solve that for x, then put those values into y= -x+ 5 to find the corresponding y.
     
  7. Mar 18, 2006 #6
    there will be equations fom which you cannot isolate X nor Y.
    there is where the sketch comes in :)
     
  8. Mar 18, 2006 #7

    Hootenanny

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    Yeah I know, but I still hate sketching graphs...could be the fact that I can't draw...:rolleyes:
     
  9. Mar 18, 2006 #8

    Integral

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    Looks like we are talking to ourselfs on this one. The OP has not been back since the origianal posts.

    Please refrain from further responses until the OP comes back.
     
  10. Mar 18, 2006 #9

    Integral

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    A hand drawn plot??? I thought everyone just used their calculator these days?
     
  11. Mar 18, 2006 #10

    Hootenanny

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    I'm still using a bog standard scientific calculator, only one step away from the abacus! If I want anything resembling an accurate plot I usually use autograph.
     
  12. Mar 18, 2006 #11

    HallsofIvy

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    Where have you gone, bambino?
     
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