How this one a function

{[ -2,-1), (-1,0), (0,1), (1,2) (2,2)}

but this one isnt

{(-4,1), (-2,1), (-2,0)

I thought functions cant have the same number appearing more than once in a relation?

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- Oct 8th 2011, 06:43 AMcytotoxictcellFunctions
How this one a function

{[ -2,-1), (-1,0), (0,1), (1,2) (2,2)}

but this one isnt

{(-4,1), (-2,1), (-2,0)

I thought functions cant have the same number appearing more than once in a relation? - Oct 8th 2011, 06:58 AManonimnystefyRe: Functions
a relation is a function if all ordered pairs have different first elements,but second can be the same.

- Oct 8th 2011, 06:58 AMSironRe: Functions
What's the definition of a function? ...

EDIT:

Anonimnystefy has given the defintion, but to be more exact, if you have given a functon $\displaystyle f:A \to B$ then:

$\displaystyle \forall a \in A, \exists! b\in B: (a,b)\in f$