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An equation expresses a relationship between (usually) two or more variables. For an equation to be a function there is only one output for each input.

For example:

In Economics, supply and demand are each represented by an equation.

Each equation has 2 variables: price (P) in dollars and quantity demanded (Q).

Demand Curve: P=16-2Q

Supply Curve: P=4+Q

A value for Q can be substituted into the equation.

When Q=4 the demand curve tells us the price P=16-2 \times 4=8

Review the use of  order of operations as well as  positive and negative numbers to ensure you evaluate the equation correctly.

Function notation:

For example:

Let B(t) denote the bank balance after t days.

B(t)= 100 + 10t

This is the function where the value of the bank balance is dependent on t, the number of days.

B(3) = 100 + 10 \times3 = 130    The value of the bank balance is 130 after 3 days.

Further information

  • Press the Printer Friendly button at the bottom left-hand corner to download a printable handout
  • RMIT University has online  videos to review the use of  equations.
  • Khan academy online videos show more details about  interpreting function notation.