Prove or disprove: For any sets X,Y,Z and any maps f:X→Y and g:Y→Z, if f is injective and g is surjective, then g ◦ f is surjective.
sorry im back to sets again. but then i realised all my workings are wrong after i gone through with my tutor on this question. i think a more strong proof would be stating an example to help me better on this. an example where f is injective and g is surjective, but gof is neither surjective nor injective, thus proving the statement is false. thanks a lot and sorry for the trouble... :(