Calculating the Balance of the Investment

Oct 13, 2025 by wbrum.org 98 views

The Function of Investment Growth: Understanding the Values of $a$ and $b$

The function $f(x) = 5,000 \cdot 1.05^x$ is a mathematical representation of an investment of $5,000 earning 5% annually. This function is an example of exponential growth, where the balance of the investment increases at a constant rate over time. In this article, we will identify and interpret the values of $a$ and $b$ in the function, and calculate the balance of the investment after 15 years.

The function $f(x) = 5,000 \cdot 1.05^x$ can be broken down into two main components: the base and the exponent. The base is 1.05, which represents the annual growth rate of 5%. The exponent is $x$ , which represents the number of years the investment has been growing.

Identifying and Interpreting the Values of $a$ and $b$

In the function $f(x) = a \cdot b^x$ , $a$ represents the initial value of the investment, and $b$ represents the growth rate. In this case, $a = 5,000$ and $b = 1.05$ .

Initial Value ( $a$ ): The initial value of the investment is $5,000. This is the amount of money that is invested at the beginning.
Growth Rate ( $b$ ): The growth rate of the investment is 5% per annum. This means that the balance of the investment increases by 5% every year.

Calculating the Balance of the Investment

To calculate the balance of the investment after 15 years, we can plug in $x = 15$ into the function:

$f(15) = 5,000 \cdot 1.05^{15}$

Using a calculator or a computer program, we can calculate the value of $f(15)$ :

$f(15) = 5,000 \cdot 1.05^{15} \approx 9,513.19$

Therefore, the balance of the investment after 15 years is approximately $9,513.19.

Interpreting the Results

The results of the calculation indicate that the investment of $5,000 earning 5% annually will grow to approximately $9,513.19 after 15 years. This represents a growth of $4,513.19 over the 15-year period.

In conclusion, the function $f(x) = 5,000 \cdot 1.05^x$ models an investment of $5,000 earning 5% annually. By identifying and interpreting the values of $a$ and $b$ , we can understand the initial value and growth rate of the investment. By calculating the balance of the investment after 15 years, we can see the impact of the growth rate on the investment over time.

The function $f(x) = a \cdot b^x$ has many applications in finance, economics, and other fields. It can be used to model population growth, compound interest, and other types of exponential growth. By understanding the values of $a$ and $b$ , we can make informed decisions about investments and other financial matters.

When working with exponential functions, it's common to make mistakes when calculating the balance of the investment. Some common mistakes include:

Incorrect calculation of the exponent: Make sure to calculate the exponent correctly, using the correct value of $x$ and the correct growth rate.
Incorrect calculation of the base: Make sure to calculate the base correctly, using the correct value of $a$ and the correct growth rate.
Incorrect calculation of the final value: Make sure to calculate the final value correctly, using the correct values of $a$ , $b$ , and $x$ .

In our previous article, we explored the function $f(x) = 5,000 \cdot 1.05^x$ , which models an investment of $5,000 earning 5% annually. We identified and interpreted the values of $a$ and $b$ , and calculated the balance of the investment after 15 years. In this article, we will answer some frequently asked questions about the function and its applications.

Q: What is the formula for calculating the balance of the investment?

A: The formula for calculating the balance of the investment is $f(x) = a \cdot b^x$ , where $a$ is the initial value of the investment, $b$ is the growth rate, and $x$ is the number of years the investment has been growing.

Q: How do I calculate the growth rate ( $b$ ) if I know the annual interest rate?

A: To calculate the growth rate ( $b$ ), you can use the formula $b = 1 + r$ , where $r$ is the annual interest rate. For example, if the annual interest rate is 5%, the growth rate would be $b = 1 + 0.05 = 1.05$ .

Q: How do I calculate the initial value ( $a$ ) if I know the current balance and the number of years the investment has been growing?

A: To calculate the initial value ( $a$ ), you can use the formula $a = \frac{f(x)}{b^x}$ , where $f(x)$ is the current balance, $b$ is the growth rate, and $x$ is the number of years the investment has been growing.

Q: What is the difference between compound interest and simple interest?

A: Compound interest is the interest earned on both the principal amount and any accrued interest over time, resulting in exponential growth. Simple interest, on the other hand, is the interest earned only on the principal amount, resulting in linear growth.

Q: How do I calculate the future value of an investment using the function $f(x) = a \cdot b^x$ ?

A: To calculate the future value of an investment using the function $f(x) = a \cdot b^x$ , you can plug in the values of $a$ , $b$ , and $x$ into the formula. For example, if the initial value is $5,000, the growth rate is 1.05, and the number of years is 15, the future value would be $f(15) = 5,000 \cdot 1.05^{15}$ .

Q: What are some common applications of the function $f(x) = a \cdot b^x$ ?

A: The function $f(x) = a \cdot b^x$ has many applications in finance, economics, and other fields, including:

Population growth: The function can be used to model population growth over time.
Compound interest: The function can be used to calculate the future value of an investment earning compound interest.
Exponential decay: The function can be used to model exponential decay, such as the decay of a radioactive substance.