All Leaving Cert Mathematics posts
• #### Functions sfjdoodjvod

Anyone know howyou tell if a functions Injective subjective or bijective?

i think injective is every x value has one y value but not every y has an x value

Surjective two different x values can give you the same y value

bijective is like a mix of the two i think... as in two x value can give one y and at the same time not every y will have an x

2. #### themathstutor.ie

For injective, every output is the image of a unique input. So you could have an element of the codomain with no corresponding element in the domain. But for those elements of the codomain with a corresponding element in the domain, there is a one-to-one relationship i.e. an element in the codomain can not be mapped from two different elements of the domain.

For surjective, the key thing is that every element in the codomain has a corresponding element in the domain, but not necessarily one-to-one.

Bijective functions fulfil the conditions of being injective and surjective. So, on-to-one mapping, and no "spare" elements in the codomain.

Check this video for a full explanation.

http://www.screencast.com/t/R37zbG88Aal