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Math Help - Math help, determine whether equation is true

  1. #1
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    Math help, determine whether equation is true

    Determine whether the following statement is true for every real numbers x
    and y:

    (x + y)^2 = x^2 + y^2
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  2. #2
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    Quote Originally Posted by fancyface View Post
    Determine whether the following statement is true for every real numbers x
    and y:

    (x + y)^2 = x^2 + y^2
    No!

    If
    x=1, y=1 it is not true.
    ---
    But let find when it is true.
    ---
    Open paranthesis,
    x^2+2xy+y^2=x^2+y^2
    Subtract,
    2xy=0
    Thus,
    xy=0
    Thus,
    x=0
    y=0

    Now if we check these two we see that it is true!
    So this is true only when one of them is zero.
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