Answer:
- first graph = NOT a function
- second graph = is a function
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Reason:
In the first graph, it is possible to draw a single vertical line through more than one point on the blue graph. For instance, draw a vertical line through 1 on the x axis.
Because this happens, we consider the graph to "fail the vertical line test". This leads to the graph not being a function.
A function is only possible if any input in the domain leads to exactly one and only one output.
The input x = 1 leads to multiple outputs y = 3 and y = -3 simultaneously.
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On the other hand, the second graph doesn't have this issue happening. It's impossible to draw a single vertical line through more than one point on the blue graph.
Therefore, this graph passes the vertical line test and it is a function. Whatever x input you pick, it leads to one y output only.