Braden bought 18 pencils for $4.50. let x represent the number of pencils purchased, and let y represent the total cost. graph the line that represents the proportional relationship.

To graph the line of the proportional relationship you should plot the points (0, 0) and (18, 4.5), and then join the points with a line.

Notice that is pretty obvious that 0 pencils cost 0 dollars, so our fist point will be (0, 0). Since x represent the number of pencils purchased and y the total cost, our second point will be (18, 4.5)

Now we can find the slope of our line using the point slope formula:

slope formula:

where  

is the slope of the line

are the coordinates of the first point on the line

are the coordinates of the second point

Since we already have our two points, we can replace the values in our formula:

Now that we have our slope, we can use the point slope formula to complete the equation of our line:

Now, to graph the line that represents the proportional relationship, we will join the points (0, 0) and (18, 4.5) using our line.

f is the midpoint of