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Question 1 (5 points)

When rabbits were introduced to the continent of Australia, they quickly multiplied and spread across the continent since there were only primitive marsupial competitors and predators to interfere with the exponential growth of their population. The data in the following table can be used to create a model of rabbit population growth.

\begin{tabular}{|l|c|c|c|c|c|}
\hline
Time (months) & 0 & 3 & 6 & 9 & 12 \\
\hline
No. of Rabbits & 6 & 32 & 107 & 309 & 770 \\
\hline
\end{tabular}

1. Find the regression equation for the rabbit population as a function of time [tex]$x$[/tex].
2. Write the regression equation in terms of base [tex]$e$[/tex].
3. Use the equation from part b to estimate the time for the rabbits to exceed 10,000.

Sagot :

To answer the given question, let's follow the steps one by one:

### 1. Find the regression equation for the rabbit population as a function of time \( x \).

We are given the data for the number of rabbits at different times in months:
- Time (months): [0, 3, 6, 9, 12]
- No. of Rabbits: [6, 32, 107, 309, 770]

We need to find the regression equation that models the population growth. Given the nature of the data, an exponential growth model will be suitable:

[tex]\[ P(t) = a \cdot e^{bt} \][/tex]

Where:
- \( P(t) \) is the population at time \( t \),
- \( a \) and \( b \) are constants to be determined.

Through regression analysis, we determine the values of \( a \) and \( b \). The optimal parameters for this model are found to be approximately:

[tex]\[ a \approx 16.70809436 \][/tex]
[tex]\[ b \approx 0.31952958 \][/tex]

### 2. Write the regression equation in terms of base \( e \).

Using the values of \( a \) and \( b \) derived from the regression analysis, the regression equation for the rabbit population as a function of time \( t \) is:

[tex]\[ P(t) = 16.70809436 \cdot e^{0.31952958t} \][/tex]

### 3. Use the equation from part (2) to estimate the time for the rabbits to exceed 10,000.

We need to find the time \( t \) when the rabbit population \( P(t) \) exceeds 10,000. So, we set up the equation:

[tex]\[ 10000 = 16.70809436 \cdot e^{0.31952958t} \][/tex]

First, isolate the exponential term:

[tex]\[ \frac{10000}{16.70809436} = e^{0.31952958t} \][/tex]

[tex]\[ 598.422 \approx e^{0.31952958t} \][/tex]

Next, take the natural logarithm of both sides to solve for \( t \):

[tex]\[ \ln(598.422) = 0.31952958t \][/tex]

[tex]\[ t = \frac{\ln(598.422)}{0.31952958} \][/tex]

Estimating the values:

[tex]\[ t \approx \frac{6.395}{0.31952958} \][/tex]

[tex]\[ t \approx 20.01206603670371 \][/tex]

Therefore, the time for the rabbit population to exceed 10,000 is approximately 20 months.