Question

compare two cell phone companies offers to see which is the better deal.





Horizon Cell Phone Company


Vertigo Cell Phone Company




Base rate=$40


Plus every minute costs $0.05

vertigo company

Base rate=$30


Plus every minute costs $0.07


Step 1: Write a linear equation of the form y1=mx+b for the Horizon Cell Phone Company. Graph this equation on the xy-plane and label it as y1. Be sure to include a large enough set of x-values (something like [0,800] would be suitable. Graphing values only from [0,10] would not yield very much information, since most cell phone users talk for more than 10 minutes each month. Also, be sure to include a title on the graph and labels on the x- and y-axes.

Step 2: Write a linear equation of the form y2=mx+b for the Vertigo Cell Phone Company. Graph this equation on the same graph. You will now have two lines on the same graph. These should intersect.

Step 3: Find the point of intersection for y1 and y2 algebraically. Show your work and also plot this point on the graph.

Step 4: Analyze which company offers a cheaper deal on cell phone costs and under what conditions. At what value are they the same?

Step 5: Suppose you talk an average of 200 minutes per month. Which is your best option? What is the difference in price between the two companies' charges for 200 minutes.