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    • Thread Starter
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    I'm having a bit of a strange time with expanding this bracket

    (ex-e-x)2

    I just can't work out why it equals

    e2x+e-2x-2

    instead of

    e2x+e-2x-1

    because when I look at each individual bit of multiplication going on,

    ex.ex=e2x

    -e-x.-e-x=e-2x

    ex.-e-x=-1

    which should therefore mean the answer is e2x+e-2x-1

    so where does that extra -1 come from?
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    (a+b)(a+b) =a^2+ab+ba+b^2 = a^2+2ab+b^2
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    Community Assistant
    (Original post by hellochaps)
    I'm having a bit of a strange time with expanding this bracket

    (ex-e-x)2

    I just can't work out why it equals

    e2x+e-2x-2

    instead of

    e2x+e-2x-1

    because when I look at each individual bit of multiplication going on,

    ex.ex=e2x

    -e-x.-e-x=e-2x

    ex.-e-x=-1

    which should therefore mean the answer is e2x+e-2x-1

    so where does that extra -1 come from?
    (a+b)^2=a^2 + b^2 + 2ab
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    When multiplying out double brackets, you do the multiplication twice, in both orders, giving two lots of -1. Same reason you get -2xy when expanding (x-y)^2
    • Thread Starter
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    oh sheesh I've literally just said the problem out loud and realised how dumb I am, yeah ignore this I think lack of sleep is getting to me :P thank you guys!
 
 
 
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Updated: April 1, 2013
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