The population of a certain city is 150,000 and is growing at [tex]$3.5\%$[/tex] each year. Write a function to model this growth.

A. [tex]\( f(x) = 150,000(1 + 0.035)^x \)[/tex]

B. [tex]\( f(x) = 150,000(1 - 0.035)^x \)[/tex]

C. [tex]\( f(x) = 3.5x + 150,000 \)[/tex]

D. [tex]\( f(x) = 0.035x + 150,000 \)[/tex]



Answer :

To model the population growth of the city, let's start by understanding the nature of the growth described in the problem.

1. Initial Population: The city's initial population is 150,000.
2. Growth Rate: The population is growing at a rate of 3.5% each year.

The formula for exponential growth is given by:

[tex]\[ f(x) = P \left(1 + r\right)^x \][/tex]

where:
- [tex]\( P \)[/tex] is the initial population,
- [tex]\( r \)[/tex] is the growth rate (expressed as a decimal),
- [tex]\( x \)[/tex] is the number of years,
- [tex]\( f(x) \)[/tex] is the population after [tex]\( x \)[/tex] years.

Plugging in the given values:
- Initial population, [tex]\(P = 150,000\)[/tex],
- Growth rate, [tex]\(r = 0.035\)[/tex] (since 3.5% = 0.035 in decimal form).

So, the function to model the growth of the city's population is:
[tex]\[ f(x) = 150,000 \left(1 + 0.035\right)^x \][/tex]

Simplifying within the parentheses:
[tex]\[ f(x) = 150,000 \left(1.035\right)^x \][/tex]

Now, let's compare this function to the given options:

1. [tex]\( f(x) = 150,000 \left(1 + 0.035\right)^x \)[/tex]
2. [tex]\( f(x) = 150,000 \left(1 - 0.035\right)^x \)[/tex]
3. [tex]\( f(x) = 3.5x + 150,000 \)[/tex]
4. [tex]\( f(x) = 0.035x + 150,000 \)[/tex]

The correct function is clearly:
[tex]\[ f(x) = 150,000 \left(1 + 0.035\right)^x \][/tex]

Upon simplifying [tex]\( 1 + 0.035 \)[/tex], we get [tex]\( 1.035 \)[/tex]. So the correct answer matches option (1):

[tex]\[ f(x) = 150,000 \left(1.035\right)^x \][/tex]