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UnderOath1617
Lv 4
UnderOath1617 asked in Science & MathematicsMathematics · 1 decade ago

onto functions?

If f: X --> Y and g: Y --> Z are functions and g º f is onto, must both f and g be onto? Prove or give a counterexample.

Any help is appreciated!

1 Answer

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  • iluxa
    Lv 5
    1 decade ago
    Favourite answer

    Counter-example:

    Let X be all integers

    Let Y be all integers in [0..99] interval

    Let Z be all integers in [0..2] interval

    let f be "x mod 10"

    let g be "y mod 3"

    f is not onto, yet g º f is onto

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