Defining the Functions q and r

Oct 13, 2025 by wbrum.org 18 views

Introduction

In mathematics, function composition is a fundamental concept that allows us to combine two or more functions to create a new function. This new function takes the output of one function as the input for another function. In this article, we will explore the concept of function composition and how to evaluate it using the given functions q and r.

Defining the Functions q and r

The functions q and r are defined as follows:

$\begin{array}{l} q(x) = 3x - 2 \\ r(x) = 2x + 1 \end{array}$

Evaluating the Composition of Functions (q ∘ r)(x)

To evaluate the composition of functions (q ∘ r)(x), we need to substitute the expression for r(x) into the expression for q(x).

$\begin{array}{l} (q ∘ r)(x) = q(r(x)) \\ = q(2x + 1) \\ = 3(2x + 1) - 2 \\ = 6x + 3 - 2 \\ = 6x + 1 \end{array}$

Evaluating the Composition of Functions (r ∘ q)(x)

To evaluate the composition of functions (r ∘ q)(x), we need to substitute the expression for q(x) into the expression for r(x).

$\begin{array}{l} (r ∘ q)(x) = r(q(x)) \\ = r(3x - 2) \\ = 2(3x - 2) + 1 \\ = 6x - 4 + 1 \\ = 6x - 3 \end{array}$

Evaluating the Composition of Functions (q ∘ r)(3)

To evaluate the composition of functions (q ∘ r)(3), we need to substitute x = 3 into the expression for (q ∘ r)(x).

$\begin{array}{l} (q ∘ r)(3) = 6(3) + 1 \\ = 18 + 1 \\ = 19 \end{array}$

Evaluating the Composition of Functions (r ∘ q)(3)

To evaluate the composition of functions (r ∘ q)(3), we need to substitute x = 3 into the expression for (r ∘ q)(x).

$\begin{array}{l} (r ∘ q)(3) = 6(3) - 3 \\ = 18 - 3 \\ = 15 \end{array}$

Conclusion

In this article, we have explored the concept of function composition and how to evaluate it using the given functions q and r. We have shown that the composition of functions (q ∘ r)(x) is equal to 6x + 1, and the composition of functions (r ∘ q)(x) is equal to 6x - 3. We have also evaluated the composition of functions (q ∘ r)(3) and (r ∘ q)(3) to be 19 and 15, respectively.

Key Takeaways

Function composition is a fundamental concept in mathematics that allows us to combine two or more functions to create a new function.
To evaluate the composition of functions, we need to substitute the expression for one function into the expression for another function.
The composition of functions (q ∘ r)(x) is equal to 6x + 1, and the composition of functions (r ∘ q)(x) is equal to 6x - 3.
The composition of functions (q ∘ r)(3) is equal to 19, and the composition of functions (r ∘ q)(3) is equal to 15.

References

[1] Larson, R. (2019). Calculus. Cengage Learning.
[2] Rogawski, J. (2019). Calculus: Early Transcendentals. W.H. Freeman and Company.
[3] Stewart, J. (2019). Calculus: Early Transcendentals. Cengage Learning.

Introduction

In our previous article, we explored the concept of function composition and how to evaluate it using the given functions q and r. In this article, we will answer some frequently asked questions about function composition to help you better understand this important mathematical concept.

Q: What is function composition?

A: Function composition is a way of combining two or more functions to create a new function. This new function takes the output of one function as the input for another function.

Q: How do I evaluate the composition of functions?

A: To evaluate the composition of functions, you need to substitute the expression for one function into the expression for another function. For example, if we want to evaluate (q ∘ r)(x), we need to substitute the expression for r(x) into the expression for q(x).

Q: What is the difference between (q ∘ r)(x) and (r ∘ q)(x)?

A: The composition of functions (q ∘ r)(x) and (r ∘ q)(x) are different because the order of the functions is reversed. In (q ∘ r)(x), we first apply the function r(x) and then apply the function q(x). In (r ∘ q)(x), we first apply the function q(x) and then apply the function r(x).

Q: How do I know which function to apply first?

A: When evaluating the composition of functions, you need to follow the order of operations. If the composition is (q ∘ r)(x), you need to apply the function r(x) first and then apply the function q(x). If the composition is (r ∘ q)(x), you need to apply the function q(x) first and then apply the function r(x).

Q: Can I have multiple functions in a composition?

A: Yes, you can have multiple functions in a composition. For example, if we have three functions p(x), q(x), and r(x), we can evaluate the composition (p ∘ q ∘ r)(x) by first applying the function r(x), then applying the function q(x), and finally applying the function p(x).

Q: How do I evaluate the composition of functions with multiple inputs?

A: When evaluating the composition of functions with multiple inputs, you need to substitute the expressions for all the functions into the expression for the new function. For example, if we have two functions p(x, y) and q(x, y), we can evaluate the composition (p ∘ q)(x, y) by first applying the function q(x, y) and then applying the function p(x, y).

Q: Can I use function composition to solve real-world problems?

A: Yes, function composition can be used to solve real-world problems. For example, if we have a function that represents the cost of producing a product and another function that represents the demand for the product, we can use function composition to find the total cost of producing the product.

Q: What are some common applications of function composition?

A: Function composition has many applications in mathematics, science, and engineering. Some common applications include:

Modeling population growth and decline
Analyzing the behavior of complex systems
Solving optimization problems
Evaluating the performance of algorithms

Conclusion

In this article, we have answered some frequently asked questions about function composition to help you better understand this important mathematical concept. We hope that this article has been helpful in clarifying any confusion you may have had about function composition.

Key Takeaways

Function composition is a way of combining two or more functions to create a new function.
To evaluate the composition of functions, you need to substitute the expression for one function into the expression for another function.
The composition of functions (q ∘ r)(x) and (r ∘ q)(x) are different because the order of the functions is reversed.
You can have multiple functions in a composition.
Function composition can be used to solve real-world problems.

References

[1] Larson, R. (2019). Calculus. Cengage Learning.
[2] Rogawski, J. (2019). Calculus: Early Transcendentals. W.H. Freeman and Company.
[3] Stewart, J. (2019). Calculus: Early Transcendentals. Cengage Learning.