Functions and Graphs
Direct proportion

Functions and Graphs

• Direct proportion
• Inverse proportion
• Rational Functions
• Testing if a relationship is a function
• Checking if an equation represents a function
• Function notation
• Composite functions
• Range and domain
• Sign diagrams​

For some linear relationships the graph passes through the origin. If this occurs we say that the two variables are in direct proportion with each other. 

If two variables are in direct proportion, they can be described by the equation y=mx, where m is the gradient of the graph and is called the proportionality constant.