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    Say there was an ordinary question about competing the square with x^2 at the front, you'd have the first 2 terms so the x^2 and the second x term. When you put those 2 terms into a bracket, would the x on the second term stay there or woud you get rid of it?

    Like this:

    (x-3x)^2 - 4
    or (x-3) - 4

    Would the x stay in the bracket or be removed?
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    (Original post by Magenta96)
    Say there was an ordinary question about competing the square with x^2 at the front, you'd have the first 2 terms so the x^2 and the second x term. When you put those 2 terms into a bracket, would the x on the second term stay there or woud you get rid of it?

    Like this:

    (x-3x)^2 - 4
    or (x-3) - 4

    Would the x stay in the bracket or be removed?
    You'd get rid of the x, but it's (x-3)^2 - 4 not (x-3) - 4.
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    (Original post by Magenta96)
    Say there was an ordinary question about competing the square with x^2 at the front, you'd have the first 2 terms so the x^2 and the second x term. When you put those 2 terms into a bracket, would the x on the second term stay there or woud you get rid of it?

    Like this:

    (x-3x)^2 - 4
    or (x-3) - 4

    Would the x stay in the bracket or be removed?
    Your wording is confusing but the second x wouldn't be there.
    For example for (x-2)^2-8
    X^2-6x-4
    The answer would be:
    (X-3)^2 -9 -4
    So (X-3)^2 -13
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    (Original post by HenryD)
    Your wording is confusing but the second x wouldn't be there.
    For example for (x-2)^2-8
    X^2-6x-4
    The answer would be:
    (X-3)^2 -6 -4
    So (X-3)^2 -10

    There is a mistake here.

    The minus 6 should be minus 9
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    (Original post by Magenta96)
    Say there was an ordinary question about competing the square with x^2 at the front, you'd have the first 2 terms so the x^2 and the second x term. When you put those 2 terms into a bracket, would the x on the second term stay there or woud you get rid of it?

    Like this:

    (x-3x)^2 - 4
    or (x-3) - 4

    Would the x stay in the bracket or be removed?

    Neither of these are correct.


    Complete the square for

    x^2 -6x -1

    Then x^2 -6x -1 = (x - 3)^2 - 3^2 -1= (x - 3)^2 - 10
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    (Original post by Magenta96)
    Say there was an ordinary question about competing the square with x^2 at the front, you'd have the first 2 terms so the x^2 and the second x term. When you put those 2 terms into a bracket, would the x on the second term stay there or woud you get rid of it?

    Like this:

    (x-3x)^2 - 4
    or (x-3) - 4

    Would the x stay in the bracket or be removed?
    Do you understand why Completing the Square works

    Do you know what the expansion of (x-3x)^2 is and what the expansion of (x-3)^2 is and why the second one is relevant to your question?
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    (Original post by steve2005)
    There is a mistake here.

    The minus 6 should be minus 9
    You're right, thanks for the correction.
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    (Original post by HenryD)
    Your wording is confusing but the second x wouldn't be there.
    For example for (x-2)^2-8
    X^2-6x-4
    The answer would be:
    (X-3)^2 -9 -4
    So (X-3)^2 -13
    Oh right yes, I know the method for completing the square, I was just wondering about the bolded bit. I always got confused if the x stayed in or was removed.

    Thanks
    • Thread Starter
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    Thanks, the equations in my question were just random examples I made up to demonstrate my point, I understand now that the x doesn't stay in the brackets. Thanks
 
 
 
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