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Math Help - Quadratic Relations and x-intercepts

  1. #1
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    Quadratic Relations and x-intercepts

    Hello, I am new here and I would like to know if someone might be able to help me with a question I am having a problem with. It is from a homework assignment that I have already received a poor mark from but unfortunately my substitute teacher is an idiot and not explaining what I did wrong to me and my actual teacher won't be back for I don't know how long.



    So with that said, I am suppose to, "state the equation of the quadratic relation for each graph and then convert it to standard form." I was able to do the first part but I am having problems understanding this one:

    y = a(x + r)(x + s)



    This thing I don't understand about this is how am I suppose to find the value for "a" I know it's probably something really simple but I just can't, for the life of me, get it.


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

    r = 5
    s = 1


    Any help would be appreciated.


    Thank you
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  2. #2
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    You have a value for x, a value for y, a value for r and a value for s. Substitute them in and you'll have an equation that you can solve for a.
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  3. #3
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    Quote Originally Posted by bonerack View Post
    Hello, I am new here and I would like to know if someone might be able to help me with a question I am having a problem with. It is from a homework assignment that I have already received a poor mark from but unfortunately my substitute teacher is an idiot and not explaining what I did wrong to me and my actual teacher won't be back for I don't know how long.



    So with that said, I am suppose to, "state the equation of the quadratic relation for each graph and then convert it to standard form." I was able to do the first part but I am having problems understanding this one:

    y = a(x + r)(x + s)



    This thing I don't understand about this is how am I suppose to find the value for "a" I know it's probably something really simple but I just can't, for the life of me, get it.


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

    r = 5
    s = 1
    So y= a(x+ 5)(x+ 1). Set x= -4 and y= -3 and you get -3= a(-4+ 5)(-4+1)= a(1)(-3) or -3= -3a. What do you think a is?


    Any help would be appreciated.


    Thank you
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  4. #4
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    Thanks to you both for the reply! I feel like a moron now because I should have known that.
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