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Math Help - transformation x^2+2x

  1. #1
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    transformation x^2+2x

    What effect does adding or subtracting x have to a graph, for example in the graph x^2+x? What if you changed it to x^2+2x, or some other co efficient, what is the transformation exactly?

    I don't think this falls into my curriculum so I can't find it in my text book, so I was just wondering !
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  2. #2
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    Quote Originally Posted by shawli View Post
    What effect does adding or subtracting x have to a graph, for example in the graph x^2+x? What if you changed it to x^2+2x, or some other co efficient, what is the transformation exactly?

    I don't think this falls into my curriculum so I can't find it in my text book, so I was just wondering !
    I'll do the easy one ...

    y = x^2+2x

    y = x^2 + 2x + 1 - 1

    y = (x+1)^2 - 1


    y = (x+1)^2 -1 is the graph of y = x^2 shifted left one unit and down one unit.
    Last edited by skeeter; October 16th 2009 at 04:57 PM. Reason: fixed errant sign ... mea culpa
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  3. #3
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    thank you

    did that only work out because it happened to be a square pattern?
    what is the transformation otherwise ?
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  4. #4
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    Quote Originally Posted by shawli View Post
    thank you

    did that only work out because it happened to be a square pattern?
    what is the transformation otherwise ?
    it worked out because I made it a "square" pattern ... the method used is called completing the square.

    it can be used for other values of linear coefficients, but is easiest if the linear coefficient value is an even number.
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  5. #5
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    Quote Originally Posted by skeeter View Post
    I'll do the easy one ...

    y = x^2+2x

    y = x^2 + 2x + 1 - 1

    y = (x-1)^2 - 1

    Shouldn't this be (x+1)^2-1 ??

    y = (x-1)^2 -1 is the graph of y = x^2 shifted right one unit and down one unit.
    I think you have the wrong sign in there.
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  6. #6
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    Quote Originally Posted by adkinsjr View Post
    I think you have the wrong sign in there.
    my mistake ... it happens
    Last edited by skeeter; October 16th 2009 at 05:19 PM.
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