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Summary

Partial Variation

• When a linear relation demonstrates partial variation, the graph is a straight line.
• The graph does not include the ordered pair (0, 0).
• The slope, or rate of change, is constant.
• A fixed value is a number that is constant and does not change.
• The fixed value in a partial variation relationship is located on the y-axis of the graph.
• The y-intercept is the point on the y-axis.

Writing the Equation of a Line

• In any direct variation relationship, the equation of the line is
  y = mx,
  where m is the slope, or rate of change.
• In any partial variation relationship, the equation of the line is
  y = mx + b,
  where m is the slope, or rate of change, and
  b is the y-intercept.
  

Drawing Graphs Given an Equation

• When drawing graphs of a given equation, ensure that
• the independent variable is on the x-axis (horizontal axis)
• the dependent variable is on the y-axis (vertical axis)
• an appropriate scale is used
• The scale must be uniform (equally spaced). Scales are selected so that the graph covers as much of the page as possible. The x-axis scale and interval size can differ from the y-axis scale and interval size.
• the points are not connected if the data is discrete
  

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