how do you know if something is not a funtion?

Question

anonymous · Answer

Is there a specific question or do you just want to know the definition?

anonymous · Answer

Which of the following does not represent a function? 

 x −2 0 1 −2 9 
y 0 −1 −2 −3 −4 


 x 3 6 9 12 18 
y 2 4 6 8 10 


 x −3 −1 0 2 4 
y −6 −4 −3 −2 −1 


 x 8 7 4 3 1 
y −7 −5 −3 −2 −1

anonymous · Answer

Okay the first way to find out f it is not a function is if there are two y values for one x value

anonymous · Answer

theres none like that?

anonymous · Answer

Yes there is, let's take a look at the first one. We have the points (-2,0), (0,-1), (1,-2), (-2,-3), (9,-4). There are two -2 x values with different y values, therefore not a function. 

The other way is to graph them and see it visually.

anonymous · Answer

ohh thanks