Question

Help i think it’s the second one but i’m not sure

Answer 1

None of the drawings is not a function.

The first drawing is the graph of the function    Y = | X | - 5 .

The second drawing is the graph of the function    Y = -X² + 6 .

The third drawing is the graph of the function   

                                        Y = (1/3) √ (21+7x) (21-7x) .

The fourth drawing is the graph of the function   Y = (2.5 ?) X - 6 .   
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They may be looking for #3 as the non-function, because it's 
a "multi-valued" function, and it has a very limited domain. 

... For each X-value, the function has two different y-values.

... 'X' is not allowed to ever be less than -3 or more than +3 .

All of this makes many people uncomfortable.

Answer 2

It's the third one. 

The second one is a parabola so that is not the answer. Hope I helped :)