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Math Help - one to one and onto

  1. #1
    Senior Member
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    one to one and onto

    Prove that
    f(x)=
    x+4 for x<=-2
    -x for -2<x<2
    x-4 for x=>2
    is onto R, but not one-to-one.

    thanks
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
    Joined
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    Quote Originally Posted by zhupolongjoe View Post
    Prove that
    f(x)=
    x+4 for x<=-2
    -x for -2<x<2
    x-4 for x=>2
    is onto R, but not one-to-one.

    thanks
    it is not 1-1 since f(-2) = f(6) and 6 is not equal to -2, obviously

    for onto, show that no matter what real number you pick, your funciton will map to it. do this piece by piece
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