Which relation is a function?

A.
{(–3, 4), (–2, 5), (0, 9), (0, 12)}

B.
{(1, 2), (1, 5), (1, –1), (1, 4)}

C.
{(7, 12), (1, –5), (3, –10), (2, –5)}

D.
{(8, –1), (2, –1), (3, 8), (2, 5}

Question

Which relation is a function?	
 
 A.
{(–3, 4), (–2, 5), (0, 9), (0, 12)}
 
 B.
{(1, 2), (1, 5), (1, –1), (1, 4)}
 
 C.
{(7, 12), (1, –5), (3, –10), (2, –5)}
 
 D.
{(8, –1), (2, –1), (3, 8), (2, 5}

anonymous · Answer

The question did not provide a chart so i dont know what it is i need to do to find the Function. Please help

geerky42 · Answer

Relation is a function if there is no x-value that pairs with more than one y-value.

unknownunknown · Answer

A function needs a unique map from independent variable : dependent variable. Check for unique x values in each case.

geerky42 · Answer

For example, it's not A since x-value 0 pairs with both 9 and 12.

anonymous · Answer

so your saying they all have to be different numbers? or no?

unknownunknown · Answer

If I ask you what x is, you must give me an answer y. You cannot give me two answers y. So each x must have a unique value y.

unknownunknown · Answer

f(x) is I mean.

anonymous · Answer

Oh.. so then it has to be different numbers.. or Values

anonymous · Answer

so then it is c?

unknownunknown · Answer

So for example, in A. We have (0, 9), and (0,12). If I ask you.. what is f(0)? Do you say.. well it's 9... or do you say it's 12? You can't give me a definite answer, so this isn't a function.

unknownunknown · Answer

Yes that's right, well done.

anonymous · Answer

Thanks!