Haley pays a monthly fee of $20 for her cell phone and then pays 5 cents per minute used. The total cost of her monthly cell phone bill can be expressed by the function [tex]\(C(m) = 0.05m + 20\)[/tex], where [tex]\(m\)[/tex] is the number of minutes used.

What are the domain and range of the function [tex]\(C(m)\)[/tex]?



Answer :

To determine the domain and range of the function [tex]\( C(m) = 0.05m + 20 \)[/tex], where [tex]\( m \)[/tex] represents the number of minutes used, we need to understand the relationship between [tex]\( m \)[/tex] and [tex]\( C(m) \)[/tex].

### Domain of the Function [tex]\( C(m) \)[/tex]

The domain of a function consists of all possible values that the independent variable (in this case, [tex]\( m \)[/tex]) can take.

1. Identify the Independent Variable: Here, [tex]\( m \)[/tex] represents the number of minutes used.
2. Consider Realistic Values for [tex]\( m \)[/tex]: Since [tex]\( m \)[/tex] represents the number of minutes used on a cell phone, it must be a non-negative integer.

Therefore, the domain of [tex]\( C(m) \)[/tex] is all non-negative integers. This can be written as:
[tex]\[ m \ge 0 \][/tex]

### Range of the Function [tex]\( C(m) \)[/tex]

The range of a function consists of all possible values that the dependent variable (in this case, [tex]\( C(m) \)[/tex]) can take.

1. Evaluate [tex]\( C(m) \)[/tex] at Its Minimum Value: Since [tex]\( m \ge 0 \)[/tex], the smallest value [tex]\( m \)[/tex] can be is 0.
[tex]\[ C(0) = 0.05 \cdot 0 + 20 = 20 \][/tex]
Therefore, the minimum value of [tex]\( C(m) \)[/tex] is 20.

2. Consider [tex]\( m \)[/tex] Increasing: As [tex]\( m \)[/tex] increases, [tex]\( C(m) \)[/tex] increases linearly. There is no upper bound for [tex]\( m \)[/tex], so [tex]\( C(m) \)[/tex] can be as large as desired.

Thus, the range of [tex]\( C(m) \)[/tex] starts from 20 and includes all values greater than or equal to 20. This can be written as:
[tex]\[ C(m) \ge 20 \][/tex]

### Summary

- Domain: The domain of [tex]\( C(m) \)[/tex] is [tex]\( m \ge 0 \)[/tex].
- Range: The range of [tex]\( C(m) \)[/tex] is [tex]\( C(m) \ge 20 \)[/tex].

So, the function [tex]\( C(m) \)[/tex] has:

- Domain: [tex]\( m \ge 0 \)[/tex]
- Range: [tex]\( C(m) \ge 20 \)[/tex], starting from the smallest value 20.0

These values summarize the constraints and behavior of Haley's cell phone bill function.

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