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Math Help - Writing related subtraction sentences.

  1. #1
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    Writing related subtraction sentences.

    ok i'm in the book prealgebra 5th edition bittinger * ellenbogen *johnson and i had to write a related addition sentences such as for 20 - 8 = 12 it would be 12+8=20 but after those problems it has " write two related subtraction sentences " and they have some of the answers in the back of the book so i know this is right for 6 + 9 = 15 its 6 =15-9 ; 9=15-6 but then i came into 8 + 0 = 8 and what i have is 8 - 0 = 8 ; 0 = 8 - 8 and i don't know if its rite or not cause the answer is not in the back of the book
    Last edited by mr fantastic; October 18th 2010 at 05:01 PM.
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  2. #2
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    It appears to be correct since you're supposed to only use the sentence components given to you.
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  3. #3
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    now it says on a question " is subtraction commutative ( is there a commutative law of subtraction ) ? why or why not ?
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  4. #4
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    Commutativity is determined by asking if x-y=h does y-x=h also?

    Think about it: 2-3 ≠ 3-2
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  5. #5
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    Quote Originally Posted by spruancejr View Post
    Commutativity is determined by asking if x-y=h does y-x=h also?

    Think about it: 2-3 ≠ 3-2
    well if your saying its not i think it has to be because 4 questions lator it asked " describe the one situation in witch subtraction is communutative "

    i still don't have the answers for ither
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  6. #6
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    Your problem states "describe the ONE situation in which subtraction is commutative". There is indeed a single case where subtraction is commutative.
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  7. #7
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    with zeros right ?
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  8. #8
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    Yes
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