How can I prove it? (injection, bijection, surjection)

[gotmejerry]

Homework Statement

How can I prove this?

If g°f is a bijective function, then g is surjective and f is injective.

Homework Equations

The Attempt at a Solution

 

[Punkyc7]

First what does g°f mean
what does bijective mean
what does surjective mean
what does injective mean

 

[Briane92]

Start of with let g of f be a bijection, than state of the definition of a bijection. From there you can prove what must be true of g and f for g of f to meet the definition.

 

[gotmejerry]

I can see why it is need to be true, when I draw it, unfotunately I cannot write down the solution in a mathematical way.

 

[Punkyc7]

To start say
Let g°f be a bijective function.

then what can you say about g°f