Question

Describe what is meant by a piecewise linear function.

Short answer

Provide an example. Answer: A piecewise linear function is a function formed by joining together linear sub-functions, each applying to a specific domain. It is related to a linear function because each sub-function within a piecewise linear function is a linear function. An example of a piecewise linear function is: f(x) = { x+2, for x < 0 -x + 4, for 0 ≤ x ≤ 4 x - 4, for x > 4 } In this example, each sub-function is a linear function with different domains.

Step-by-step solution

Definition of a Piecewise Function

A piecewise function is a function that is defined by multiple sub-functions, each applying to a different domain (a part of the x-values). In other words, a piecewise function is described by different rules or expressions for different intervals of its domain. The main goal is to represent functions that have different behaviors and structures in different parts of their domain.

Definition of a Linear Function

A linear function is a function with a constant rate of change. It can be represented with the equation y = mx + b, where m represents the slope, and b represents the y-intercept. The slope determines the angle in which the line appears relative to the x-axis, and the y-intercept determines where the line intersects the y-axis.

Piecewise Linear Function

A piecewise linear function is a function formed by joining together linear sub-functions, each applying to a specific domain. In other words, it is a piecewise function where each sub-function is a linear function.

Example of a Piecewise Linear Function

Let's consider a piecewise linear function with the following definition: f(x) = \begin{cases} x+2, & \text{for } x < 0 \\ -x + 4, & \text{for } 0 \leq x \leq 4 \\ x - 4, & \text{for } x > 4 \\ \end{cases} In this example, there are three linear sub-functions: 1. For x < 0, the function has a slope of 1 and a y-intercept of 2 (y = x + 2). 2. For 0 ≤ x ≤ 4, the function has a slope of -1 and a y-intercept of 4 (y = -x + 4). 3. For x > 4, the function has a slope of 1 and a y-intercept of -4 (y = x - 4). Thus, this function is a clear example of a piecewise linear function, as it is composed of linear functions over three different domains.

Key concepts

Piecewise Function

A piecewise function is an intriguing type of function that you'll likely encounter when dealing with different behaviors over distinct intervals. Consider it as a mathematical chameleon that adapts its appearance based on the range (or domain) it covers.

To break it down: a piecewise function is defined by a collection of sub-functions. Each sub-function applies to a particular interval of the domain. This essentially means the overall function can switch its pattern depending on which part of the x-axis you're examining.

• It's like having a collection of rules—one rule for this part of the domain and another rule for that part.
• Think of dividing a movie into segments, with each segment having its unique director. The story might feel different in each segment, although it's still part of the same movie.
• The piecewise function helps to model scenarios where behavior changes at certain points, like a tax rate that varies with income.

Understanding piecewise functions is vital, especially when representing real-world phenomena or more complex mathematical relationships that aren't simply linear or constant across all x-values.

Linear Function

A linear function is the simplest form of a function that yields a straight line when graphed. You can think of it as a perfect straight trail in a park that neither twists nor changes height abruptly.

In mathematical terms, a linear function is represented by the equation \( y = mx + b \). Here:

• \( m \) is the slope: It tells you how steep the line is and its direction (upward or downward).
• \( b \) is the y-intercept: It tells you the point on the y-axis where the line crosses.
• This type of function exhibits a consistent rate of change—that is, for every unit change in \( x \), the change in \( y \) remains constant.

Linear functions are fundamental in math because they help us understand the basic relationship between variables, where an increase or decrease in one affects the other uniformly.

Domain

The domain of a function refers to the complete set of possible input values (usually x-values) that a function can accept. In simpler terms, it's like knowing the list of ingredients you can choose from when following a recipe.

For all functions—whether they are linear, piecewise, or nonlinear—it’s important to grasp their domains because:

• This tells us where the function is defined and working properly.
• The domain allows us to pinpoint intervals that each piece of a function can work on, especially in the case of piecewise functions.
• Understanding the domain prevents us from plugging in values that might lead to undefined situations, such as division by zero or the square root of a negative number.

In the example of a piecewise linear function, each sub-function handles a specific portion of the domain, ensuring we achieve the right output based on the right input each time.