Answer:
a) linear. Cost per minute is a constant.
b) f(x) = 40 -0.15x
d) f(100) = 25. The remaining value is $25 after using 100 minutes.
Step-by-step explanation:
a) Since the cost per minute is a constant, the remaining dollar value of the phone decreases by the same amount for each minute used. The cost as a function of minutes used is a linear function with a constant rate of change.
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b) The value starts at $40 and decreases by $0.15 for each increment of x (minutes used). The function can be written as ...
f(x) = 40 -0.15x
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d) Put 100 where x is in the function definition and do the arithmetic.
f(100) = 40 -0.15×100 = 40 -15
f(100) = 25
According to the variable and function definitions, x=100 means 100 minutes have been used; f(x) = 25 means the remaining value of the phone is 25 dollars.
f(100) = 25 means the phone's remaining value is $25 when 100 minutes have been used.
