Unit D: Graphing


Linear Relationships

A relation is one way to show a relationship between variables or sets of data. Graphing relations is a way of using pictures to represent relationships between two quantities. A line graph is a type of relation that can be classified as one of the following:

  • a straight line
  • a curved line
  • no relationship




A graph is considered to be linear if and only if the points form a straight line.



Straight line


Straight line
Both graphs consist of a straight line so these are examples of linear relations.


The graph below is a non-linear relation since the graph does not consist of a straight line.






Non- Linear Relation: Curved line 

If the points seem to be scattered everywhere without any connection, then it is not a relation.


Points without a pattern (no correlation)


 
Label the following graphs as a linear relation, a non-linear relation, or not a relation.

a.
Graph a is a non-linear relation because the line drawn is not straight, but a general trend can be seen.



b.
Graph b is a linear relation because the line drawn is straight, and a general trend can be seen.



c.
Graph c is a not a relation since the points plotted do not appear to have any relationship with each other.




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