y = 25+10x or y = 10x+25
y = 18 + 15x or y = 15x + 18
Here are you two equations.
to solve by substitution
10x + 25 = 15x + 18 Solve for y and then find x.
Two cell phone companies have different rate plans.Runfast has monthly charges $25 plus $10 per gig of data.B A&D’s monthly charge is $18 plus 15 per gig of data. Your task is to determine under what circumstances each company has the better pricing. You will derive and solve a set of equations, graph those equations, and evaluate the meanings for these events. Don’t worry; I have a series of questions to guide you through the process. Good luck!
1. Determine the equation for the monthly charges for Runfast and B A&D.
Runfast= ______________________
BA&D=________________________
2. Use your mathematical skill to solve this system of equations using the substitution method. (Show your work here.)
3. Graph the results on the accompanying graph as a visual aid. Don’t forget to label which line is for which company.
4. Why don’t the lines start at the origin?_______________________________________________
5. What is special about each of the y-intercepts?________________________________________
6. Which company has the better deal for customers that don’t us much data? How do you know?________________________________________________________
7. At what point are the plans the same amount? How do you know?____________________________
8. Which company has the better deal for customers that use a lot of data? How do you know?_______________________________________________
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