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Standard form of a Parabola

  1. Apr 14, 2008 #1
    Change the equation to standard form.

    y = x^2 + 8x + 20


    I thought this was the standard form for parabolas?? I tried this as the answer but it said it was wrong

    y = (x+4)^2 +4

    Thanks for the help! :-)
     
  2. jcsd
  3. Apr 14, 2008 #2

    symbolipoint

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    Complete the Square to the general form of the equation (and then undo this) and you will have something which is factorable. For your exercise, you want to add and subtract (8/2)^2 , and I will leave the rest of this for your effort to continue.
     
  4. Apr 14, 2008 #3
    okay so completing the square gives me

    y = x^2 +8x + 20 + 16 - 16
    y = (x^2 + 8x +16) + 4
    then factor...

    y = (x + 4)^2 + 4

    which is exactly what I got before???
     
  5. Apr 14, 2008 #4

    symbolipoint

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    That appears to be correct. That IS the standard form for your equation given in your exercise. The parabola has been shifted upward by 4 units and to the left by 4 units from standard position.
     
  6. Apr 14, 2008 #5
    okay thanks...I'll ask the teacher then, its an online submission homework so maybe somethings wrong. hopefully.
     
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