Question

Talk the Talk Cellular charges a base rate of $20 per month for unlimited texts plus $.15 per minute of talk time. Write an equation, in function notation, to represent this situation and state a reasonable domain and range.

Answer 1

y = 20 + 0.15x

where x = each minute of talk time

y = total cost

domain [0, ∞)

range [20, ∞)

Explanation:

Your equation is like that because you always pay $20 per month, no matter how many minutes you used. Then you have 0.15 per minute so use x as a variable placeholder for the actual number of minutes.

domain is starting from 0 because you can't have negative minutes.

range is at least 20 because you pay $20 to use it even if you don't use any minutes. So it can't be less than $20.