Is g of f Injective or Surjective When f and g Are Functions?

[QuantumDefect]

Hello, I need some help. Could someone kick me(hard please) in the right direction here? Here are the statements I need to prove:
1) If g of f is injective, then f is injective
2) If g of f is subjective, then g is subjective

where g and f are functions where f:A->B and g:B -> C where A,B and C are sets

Any kicks in the right direction would be GREATLY appreciated. Thank you.

 

[Treadstone 71]

Both can be done easily by contradiction.

 

[Curious3141]

Start with the definitions of injections and surjections (note the spelling of the latter), and draw functional mappings (domain/codomain diagrams). The proof is fairly easy from inspecting the mappings.

Wikipedia has fairly good pages on these subjects, complete with the mappings you need for the proof : http://en.wikipedia.org/wiki/Injective_function

http://en.wikipedia.org/wiki/Surjection