U03_L2_T1_we2 Representing Functions as Graphs  Summary and Q&A
TL;DR
The points on the graph do not represent a function because one xvalue is mapped to two different yvalues.
Questions & Answers
Q: How is a function defined?
A function takes an input (usually x) and maps it to an output value. It should either produce a unique yvalue for every xvalue or be undefined for certain xvalues.
Q: Can a function map one xvalue to multiple yvalues?
No, a function should map each xvalue to only one yvalue. Having multiple yvalues for the same xvalue violates the definition of a function.
Q: Why is the point (6, ?) undefined in the given graph?
The point (6, ?) is undefined because the function has not been defined or specified for the xvalue of 6.
Q: Why do the points on the graph not represent a function?
The points on the graph do not represent a function because an xvalue of 4 is mapped to both 1 and 5, violating the requirement for a function to have a unique output value for each input value.
Summary & Key Takeaways

A function takes an input (usually denoted as x) and maps it to an output value, which is typically represented as f(x) or y.

For the points on the given graph to represent a function, there should be a unique yvalue for every xvalue, or the function should be undefined for certain xvalues.

In the given graph, an xvalue of 4 is mapped to both 1 and 5, violating the requirement for a function.