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How do I prove that ac<bd?

How do I prove that ac<bd given the conditions that a,b,c,d are integers and 0<a<b and 0<c<d?

Update:

Has to use the Axioms for Integer, division is not allowed, only the basic operations of addition and multiplication.

3 Answers

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  • ?
    Lv 7
    1 decade ago
    Favorite Answer

    Since 0<a<b and c is positive, ac < bc

    Since 0<c<d and b is positive, bc < bd

    By the transitive property, ac < bc and bc < bd implies ac < bd

  • 1 decade ago

    Given: 0 < a < b, 0 < c < d

    Prove ac < bd

    a / b < d / c

    Since a < b, a / b < 1.

    Since c < d, d / c > 1

    Therefore

    a / b < 1 < d / c

    and so

    ac < bd

    Pretty simple algebraic proof.

  • wilde
    Lv 4
    4 years ago

    Prove A B

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