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Quadratic in standard form help please

  1. Mar 15, 2007 #1
    Quadratic in standard form help....please

    1. The problem statement, all variables and given/known data

    Write the quadratic function f(x) = x^2 + 3x + 2 in standard form.

    2. Relevant equations

    Standard form equation : f(x) = a(x-h)^2 + k


    3. The attempt at a solution

    Ok, I think I got this one but am wanting to be sure.

    I set it up : (x^2 + 3x + 2.25) + 2

    then get : (x + 1.5)^2 + 2 - 2.25

    then get as answer : f(x) = (x + 1.5)^2 - .25

    Is this what you all get ? :smile:

    I really appreciate any help.
     
  2. jcsd
  3. Mar 15, 2007 #2
    Where did the 2.25 come from?
     
  4. Mar 15, 2007 #3

    cristo

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    Staff Emeritus
    Science Advisor

    That looks fine to me. If you want to check in future, expand out the bracket, and simplify. What you get should be equal to the original expression.

    Edit: I didn't read any lines other than the last one! The final answer is correct, however the method doesn't make much sense (I'm glad someone's on the ball, neutrino! :smile: )
     
    Last edited: Mar 15, 2007
  5. Mar 15, 2007 #4
    Take half of three and multiply it by itself.
     
  6. Mar 15, 2007 #5
    Thanks cristo ! I am checking it now. It works out :) Thanks for the tip.
     
    Last edited: Mar 15, 2007
  7. Mar 15, 2007 #6
    Okay, but it can't magically appear from nowhere, can it? :wink: You add and subtract that amount, so that the expression x^2+3x+2 +2.25 -2.25 is equivalent to x^2+3x+2.
     
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