You just bought a cell phone for $14.99. 100 minutes for your phone, including tax, cost $21.99 per month.

Write a linear function that models buying the phone and minutes then use that equation to determine the cost of the phone and twelve months of service.

Question

You just bought a cell phone for $14.99.  100 minutes for your phone, including tax, cost $21.99 per month.  

Write a linear function that models buying the phone and minutes then use that equation to determine the cost of the phone and twelve months of service.

anonymous · Answer

The equation of a line is y = mx+b.  As far as costs are concerned, M is the part that you keep paying for, and B is the part you only pay once.

So: y = 21.99x+14.99

To find how much it costs after 12 months of service, just substitute 12 for x, and you get:

y = (21.99)(12) + 14.99

anonymous · Answer

thank you (: