A biologist is studying the exponential growth of a colony of bacterial cells. The table gives the number of cells, [tex][tex]$y$[/tex][/tex], in the colony over time, [tex][tex]$x$[/tex][/tex], in hours.

\begin{tabular}{|c|c|}
\hline Time, [tex][tex]$x$[/tex][/tex] (hours) & Number of Cells, [tex][tex]$y$[/tex][/tex] \\
\hline 0 & 100 \\
\hline 1 & 200 \\
\hline 2 & 400 \\
\hline [tex][tex]$h$[/tex][/tex] & 6,400 \\
\hline
\end{tabular}

Replace the values of [tex][tex]$A, b, x$[/tex][/tex], and [tex][tex]$y$[/tex][/tex] to write an exponential equation that represents the number of cells present at [tex][tex]$h$[/tex][/tex] hours.



Answer :

To determine the values of [tex]\( A \)[/tex], [tex]\( b \)[/tex], [tex]\( x \)[/tex], and [tex]\( y \)[/tex] in the exponential growth equation for the bacterial cells, follow these steps:

1. Identifying the General Form of the Exponential Growth Equation:
An exponential growth equation typically has the form:
[tex]\[ y = A \cdot b^x \][/tex]
where
- [tex]\( y \)[/tex] is the number of bacterial cells,
- [tex]\( A \)[/tex] is the initial amount of cells,
- [tex]\( b \)[/tex] is the base representing the growth factor,
- [tex]\( x \)[/tex] is the time in hours.

2. Determine the Initial Amount of Cells ([tex]\(A\)[/tex]):
From the given data, at time [tex]\( x = 0 \)[/tex] hours, the number of cells [tex]\( y \)[/tex] is 100. Therefore, the initial amount ([tex]\( A \)[/tex]) is:
[tex]\[ A = 100 \][/tex]

3. Calculate the Growth Factor ([tex]\(b\)[/tex]):
We can use the data from [tex]\( x = 0 \)[/tex] and [tex]\( x = 1 \)[/tex] to find [tex]\( b \)[/tex]:
- At [tex]\( x = 0 \)[/tex] hours, [tex]\( y = 100 \)[/tex]
- At [tex]\( x = 1 \)[/tex] hour, [tex]\( y = 200 \)[/tex]

The equation at [tex]\( x = 1 \)[/tex] hour is:
[tex]\[ 200 = 100 \cdot b \][/tex]
Solving for [tex]\( b \)[/tex]:
[tex]\[ b = \frac{200}{100} = 2 \][/tex]

4. Identify the Exponential Equation:
Substitute [tex]\( A = 100 \)[/tex] and [tex]\( b = 2 \)[/tex] into the general form. The exponential equation for the number of cells is:
[tex]\[ y = 100 \cdot 2^x \][/tex]

5. Find the Number of Hours ([tex]\(h\)[/tex]) Needed for 6400 Cells:
When [tex]\( y = 6400 \)[/tex], we need to solve for [tex]\( x \)[/tex] (which we denote as [tex]\( h \)[/tex]):
[tex]\[ 6400 = 100 \cdot 2^h \][/tex]
First, divide both sides by 100:
[tex]\[ 64 = 2^h \][/tex]
Using properties of exponents, we know:
[tex]\[ 2^6 = 64 \][/tex]
Thus,
[tex]\[ h = 6 \][/tex]

6. Final Exponential Equation:
Based on the calculated values, the exponential equation for the growth of the bacterial cells, accounting for the given values, is:
[tex]\[ y = 100 \cdot 2^x \][/tex]
Specifically, for [tex]\( h = 6 \)[/tex]:
[tex]\[ 6400 = 100 \cdot 2^6 \][/tex]

Therefore, this detailed, step-by-step solution shows that the values for [tex]\( A, b, h \)[/tex], and [tex]\( y \)[/tex] are 100, 2, 6, and 6400, respectively, in the context of exponential growth of bacterial cells.