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Math Help - Distributive property help

  1. #1
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    Post Distributive property help

    I have a test tommorow and Im in grade 8 algebra 1
    Could somebody walk me through these 2 questions so i know if im doing it right or not?
    2(1-d) - (2d+1)

    5(2-j) + (2j-3)


    Cheers,
    Sam
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  2. #2
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    Let's look at 5(2-j) + (2j-3). I'll insert the implied multiplication sign to write 5 x (2-j) + (2j-3). We do the multiplication first (BODMAS). 5 x (2-j): multiplication distributes over addition, that is, a x (b+c) = (a x b) + (a x c), inserting () for clarity. Equally x distributes over -. So 5 x (2-j) = 5x2 - 5xj = 10 - 5j. So the total expression is (10 - 5j) + (2j - 3). We can gather terms (repeatedly using associative and commutative properties) to get (2j-5j) + (10-3). Reversing the distributive law 2j-5j = (2-5)j = -3j. So the answer is7 - 3j.
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  3. #3
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    thnx

    2(1-d) - (2d+1)

    When multiplying the second equation is it -1x2d and -1x1
    Last edited by why-do-i-have-to-register; August 18th 2005 at 04:01 PM.
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  4. #4
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    Quote Originally Posted by why-do-i-have-to-register
    2(1-d) - (2d+1)

    When multiplying the second equation is it -1x2d and -1x1
    Yes, it is.
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