Rational Functions and Function Models Graded Assignment

1. Evaluate

The table below gives the change in function values for the functions [tex]$f$[/tex], [tex]$g$[/tex], and [tex]$h$[/tex] for certain intervals of [tex]$x$[/tex]. Consider the information in the table, then answer the questions below.

\begin{tabular}{|r|r|r|r|r|r|}
\hline & [tex]$0 \leq x\ \textless \ 1$[/tex] & [tex]$1 \leq x\ \textless \ 2$[/tex] & [tex]$2 \leq x\ \textless \ 3$[/tex] & [tex]$3 \leq x\ \textless \ 4$[/tex] & [tex]$4 \leq x\ \textless \ 5$[/tex] \\
\hline Change in [tex]$f(x)$[/tex] & 3.1 & 3.8 & 4.0 & 4.2 & 4.4 \\
\hline Change in [tex]$g(x)$[/tex] & 2.1 & 1.9 & -4.0 & -4.1 & -4.1 \\
\hline Change in [tex]$h(x)$[/tex] & 3.3 & 3.1 & 2.9 & 2.7 & 2.5 \\
\hline
\end{tabular}

a) State an appropriate domain and range for [tex]$f(x)$[/tex]. If the domain or range cannot be determined, explain. [10 points]

b) Determine the rate of change for [tex]$f(x)$[/tex] on the sub-interval [tex]$2 \leq x\ \textless \ 5$[/tex]. Circle one. [10 points]
- 0.4
- 4.2
- Cannot be determined

c) Which of the functions is best modeled by a piecewise-linear function with two linear segments with different slopes? [5 points]



Answer :

Let's solve the question step-by-step as a math teacher.

### Part a) State an appropriate domain and range for [tex]\( f(x) \)[/tex]

To determine the domain for [tex]\( f(x) \)[/tex], we observe the intervals given in the table. The intervals for [tex]\( x \)[/tex] are [tex]\( 0 \leq x < 1 \)[/tex], [tex]\( 1 \leq x < 2 \)[/tex], [tex]\( 2 \leq x < 3 \)[/tex], [tex]\( 3 \leq x < 4 \)[/tex], and [tex]\( 4 \leq x < 5 \)[/tex]. Collectively, these intervals cover [tex]\( 0 \leq x < 5 \)[/tex]. Hence, the domain of [tex]\( f(x) \)[/tex] is:

[tex]\[ \text{Domain of } f(x): \quad 0 \leq x < 5 \][/tex]

To determine the range for [tex]\( f(x) \)[/tex], we need to examine how [tex]\( f(x) \)[/tex] changes across these intervals.

- Let's assume [tex]\( f(0) = 0 \)[/tex] for simplicity.
- From [tex]\( 0 \leq x < 1 \)[/tex], [tex]\( f(x) \)[/tex] increases by 3.1, so [tex]\( f(1) = 3.1 \)[/tex].
- From [tex]\( 1 \leq x < 2 \)[/tex], [tex]\( f(x) \)[/tex] increases by 3.8, so [tex]\( f(2) = 3.1 + 3.8 = 6.9 \)[/tex].
- From [tex]\( 2 \leq x < 3 \)[/tex], [tex]\( f(x) \)[/tex] increases by 4.0, so [tex]\( f(3) = 6.9 + 4.0 = 10.9 \)[/tex].
- From [tex]\( 3 \leq x < 4 \)[/tex], [tex]\( f(x) \)[/tex] increases by 4.2, so [tex]\( f(4) = 10.9 + 4.2 = 15.1 \)[/tex].
- From [tex]\( 4 \leq x < 5 \)[/tex], [tex]\( f(x) \)[/tex] increases by 4.4, so [tex]\( f(5) = 15.1 + 4.4 = 19.5 \)[/tex].

Therefore, the range of [tex]\( f(x) \)[/tex] as [tex]\( x \)[/tex] varies from [tex]\( 0 \leq x < 5 \)[/tex] is:

[tex]\[ \text{Range of } f(x): \quad 0 \leq f(x) \leq 19.5 \][/tex]

### Part b) Determine the rate of change for [tex]\( f(x) \)[/tex] on the sub-interval [tex]\( 2 \leq x < 5 \)[/tex]

To calculate the rate of change for [tex]\( f(x) \)[/tex] on the sub-interval [tex]\( 2 \leq x < 5 \)[/tex], we consider the intervals [tex]\( 2 \leq x < 3 \)[/tex], [tex]\( 3 \leq x < 4 \)[/tex], and [tex]\( 4 \leq x < 5 \)[/tex].

The changes in [tex]\( f(x) \)[/tex] in these intervals are:
- For [tex]\( 2 \leq x < 3 \)[/tex], the change is 4.0.
- For [tex]\( 3 \leq x < 4 \)[/tex], the change is 4.2.
- For [tex]\( 4 \leq x < 5 \)[/tex], the change is 4.4.

The average rate of change in these intervals:
[tex]\[ \text{Rate of Change} = \frac{4.0 + 4.2 + 4.4}{3} = \frac{12.6}{3} = 4.2 \][/tex]

So, the rate of change for [tex]\( f(x) \)[/tex] on the interval [tex]\( 2 \leq x < 5 \)[/tex] is:

[tex]\[ 4.2 \][/tex]

### Part c) Which of the functions is best modeled by a piecewise-linear function with two linear segments with different slopes?

To decide which function is best modeled by a piecewise-linear function with two linear segments with different slopes, we need to analyze the changes in each function over the intervals.

- [tex]\( f(x) \)[/tex] shows consistent positive changes (3.1, 3.8, 4.0, 4.2, 4.4). This indicates a single increasing slope with slight variation but not distinctively two different slopes.
- [tex]\( g(x) \)[/tex] changes as (2.1, 1.9, -4.0, -4.1, -4.1). Initially, there is a positive slope (increasing), followed by a negative slope (decreasing).
- [tex]\( h(x) \)[/tex] changes as (3.3, 3.1, 2.9, 2.7, 2.5). This shows a consistently decreasing rate but not distinctly two linear segments with different slopes.

Thus, [tex]\( g(x) \)[/tex] is best modeled by a piecewise-linear function with two linear segments with different slopes because it shows a distinct increase initially and then a consistent decrease.

In conclusion:
- Domain of [tex]\( f(x) \)[/tex]: [tex]\( 0 \leq x < 5 \)[/tex]
- Range of [tex]\( f(x) \)[/tex]: [tex]\( 0 \leq f(x) \leq 19.5 \)[/tex]
- Rate of change for [tex]\( f(x) \)[/tex] on [tex]\( 2 \leq x < 5 \)[/tex]: [tex]\( 4.2 \)[/tex]
- Function best modeled by a piecewise-linear function with two linear segments with different slopes: [tex]\( g(x) \)[/tex]