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    X Squared - 49


    how do u factorise this into brackets
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    (Original post by Sabhani2000)
    X Squared - 49


    how do u factorise this into brackets
    (x + 7)(x -7)
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    (Original post by Sabhani2000)
    X Squared - 49


    how do u factorise this into brackets
    The difference of two squares
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    (Original post by Sage25)
    (x + 7)(x -7)
    how did u work that out?
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    (Original post by sage25)
    the difference of two squares

    thank you!!
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    There's no b value (ie a number of x's eg 4x) so you know that it must be difference of two squares because if you expand it out in a square they cancel out eg +7x and -7x. You then just find the square root of c (49) which is 7 and one of them must be negative if its -49
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    (Original post by Sabhani2000)
    how did u work that out?
    The co-efficient of x^2 is 1

    so it would be have to be two single x's in the brackets like (x + a)(x + b)

    Then, as the number at the end is -49, and there is no value of x it would mean a and b have to multiply to get -49 and add together to get 0

    So, 7 x -7 = -49

    And

    7 + (-7) = 0

    Therefore x^2 - 49 = (x + 7) (x - 7)
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    (Original post by sage25)
    the co-efficient of x^2 is 1

    so it would be have to be two single x's in the brackets like (x + a)(x + b)

    then, as the number at the end is -49, and there is no value of x it would mean a and b have to multiply to get -49 and add together to get 0

    so, 7 x -7 = -49

    and

    7 + (-7) = 0

    therefore x^2 - 49 = (x + 7) (x - 7)
    ow ok now i understand !
    Thanks for the help!
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    (Original post by Sabhani2000)
    ow ok now i understand !
    Thanks for the help!
    No problem!
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    \displaystyle

\begin{equation*}a^2 - b^2 = (a+b)(a-b)\end{equation*}
 
 
 
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