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Math Help - set theory

  1. #1
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    set theory

    give an example of sets X and Y such that X cross Y not equal Y cross X

    give sets such that Xcross(YcrossZ) not equal (XcrossY)crossZ

    probably too late
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by jbpellerin View Post
    give an example of sets X and Y such that X cross Y not equal Y cross X
    take your pic! any once X and Y are different sets (both non-zero) the cross-product would not commute. make X and Y different sizes to make sure.

    give sets such that Xcross(YcrossZ) not equal (XcrossY)crossZ

    probably too late
    again, pick pretty much any different sets for X, Y and Z. the chances of you getting one that doesn't work here are slim
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