To figure out whether a graph is a function, you need to use the line test. The line test is where you pass a vertical line over the graph. If the vertical line crosses the graph more than once, the graph is not a function. You can use your pencil as a vertical line.
Graph 1 is not a function because the vertical line will cross the graph twice.
Graph 2 is a function because the vertical does not cross the graph twice.
Graph 3 is not a function because the vertical line will cross the graph twice.
T= 21.79x + 3.99x + 6.89x where t is the total cost and x is the number of brushes/rollers/paint cans you buy. You don't need a different variable for each item because you buy the same amount of each.
