U03_L2_T1_we2 Representing Functions as Graphs | Summary and Q&A

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July 29, 2010
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Khan Academy
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U03_L2_T1_we2 Representing Functions as Graphs

TL;DR

The points on the graph do not represent a function because one x-value is mapped to two different y-values.

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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 y-value for every x-value or be undefined for certain x-values.

Q: Can a function map one x-value to multiple y-values?

No, a function should map each x-value to only one y-value. Having multiple y-values for the same x-value 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 x-value 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 x-value 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 y-value for every x-value, or the function should be undefined for certain x-values.

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

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