The Graph Of Is Shown. Draw The Graph Of

Let's delve into the fascinating world of function transformations, specifically focusing on how the graph of y = f(x) dictates the shape and position of the graph of y = |f(x)|. This exploration will not only sharpen your understanding of mathematical functions but also provide you with a valuable tool for visualizing and manipulating graphs.

Understanding the Base Function: y = f(x)

Before we can understand the transformation, we need a solid grasp of what the original function, y = f(x), represents. In its most basic form, f(x) is a rule or formula that assigns a single output value y to each input value x. The graph of y = f(x) is the visual representation of all these (x, y) pairs plotted on a coordinate plane.

The nature of f(x) can vary widely. It could be a simple linear function like f(x) = 2x + 1, a quadratic function like f(x) = x² - 3x + 2, a trigonometric function like f(x) = sin(x), an exponential function like f(x) = e^x, or even a more complex piecewise function. The specific form of f(x) determines the overall shape and characteristics of its graph.

Key aspects of y = f(x) to consider include:

Domain: The set of all possible x-values for which the function is defined.
Range: The set of all possible y-values that the function can produce.
Intercepts: The points where the graph crosses the x-axis (x-intercepts or roots) and the y-axis (y-intercept).
Symmetry: Whether the graph is symmetric about the y-axis (even function), the origin (odd function), or neither.
Asymptotes: Lines that the graph approaches as x approaches infinity or negative infinity (horizontal asymptotes) or as x approaches a specific value (vertical asymptotes).
Increasing/Decreasing Intervals: The intervals of x-values where the function is increasing or decreasing.
Local Maxima/Minima: The highest and lowest points on the graph within a specific interval.

Introducing the Absolute Value Transformation: y = |f(x)|

Now, let's introduce the absolute value transformation. The function y = |f(x)| takes the original function f(x) and applies the absolute value operation to its output. Remember that the absolute value of a number is its distance from zero, regardless of its sign. Therefore, |x| = x if x ≥ 0, and |x| = -x if x < 0.

This seemingly simple transformation has a profound effect on the graph. The key change is that it ensures all y-values are non-negative. Any portion of the graph of y = f(x) that lies below the x-axis (i.e., where f(x) < 0) is reflected across the x-axis, effectively "flipping" it upwards. The portion of the graph that lies above the x-axis (i.e., where f(x) ≥ 0) remains unchanged.

In summary:

If f(x) ≥ 0, then |f(x)| = f(x), and the graph remains the same.
If f(x) < 0, then |f(x)| = -f(x), and the graph is reflected across the x-axis.

Step-by-Step Guide to Graphing y = |f(x)| from y = f(x)

Here's a systematic approach to drawing the graph of y = |f(x)| given the graph of y = f(x):

Start with the Graph of y = f(x): Obtain or sketch the graph of the original function y = f(x). This is your starting point.
Identify the x-intercepts: Find all the points where the graph of y = f(x) intersects the x-axis. These are the points where f(x) = 0. These points will remain unchanged in the graph of y = |f(x)| because |0| = 0. They act as "hinges" or pivot points for the reflection.
Identify Regions Where f(x) < 0: Determine the intervals of x-values where the graph of y = f(x) lies below the x-axis. These are the regions where the y-values are negative.
Reflect the Negative Regions: For each interval where f(x) < 0, reflect the corresponding portion of the graph across the x-axis. This means that for every point (x, y) in the negative region, replace it with the point (x, -y). Imagine folding the graph along the x-axis and tracing the reflection.
Leave the Non-Negative Regions Unchanged: The portions of the graph of y = f(x) that lie on or above the x-axis (where f(x) ≥ 0) remain exactly the same in the graph of y = |f(x)|.
Combine the Reflected and Unchanged Portions: The graph of y = |f(x)| consists of the reflected portions (from step 4) and the unchanged portions (from step 5).
Erase the Original Graph (Optional): To avoid confusion, you can erase the original graph of y = f(x), leaving only the graph of y = |f(x)|.

Example 1: f(x) = x

y = f(x) = x is a straight line passing through the origin with a slope of 1.
For x < 0, f(x) < 0. This portion of the line (the part in the third quadrant) is reflected across the x-axis.
For x ≥ 0, f(x) ≥ 0. This portion of the line (the part in the first quadrant) remains unchanged.
The resulting graph of y = |x| is a "V" shape with its vertex at the origin.

Example 2: f(x) = sin(x)

y = f(x) = sin(x) is the standard sine wave oscillating between -1 and 1.
The x-intercepts are at x = nπ, where n is an integer.
The portions of the sine wave below the x-axis are reflected across the x-axis.
The resulting graph of y = |sin(x)| consists of a series of humps, all above the x-axis. The range is now [0, 1] instead of [-1, 1].

Example 3: f(x) = x² - 4

y = f(x) = x² - 4 is a parabola opening upwards with x-intercepts at x = -2 and x = 2 and a y-intercept at y = -4.
The portion of the parabola between x = -2 and x = 2 lies below the x-axis. This portion is reflected across the x-axis.
The resulting graph of y = |x² - 4| looks like a "W" shape.

Properties of y = |f(x)|

Understanding how the absolute value transformation affects the properties of the original function is crucial.

Range: The range of y = |f(x)| is always a subset of [0, ∞). This is because the absolute value ensures that all y-values are non-negative. If the range of f(x) is [a, b] where a < 0 and b > 0, then the range of |f(x)| is [0, max(|a|, b)].
Non-negativity: By definition, y = |f(x)| ≥ 0 for all x in the domain of f(x).
Symmetry: If f(x) is an even function (i.e., f(-x) = f(x)), then |f(x)| is also an even function. This is because |f(-x)| = |f(x)|. However, if f(x) is an odd function (i.e., f(-x) = -f(x)), then |f(x)| is generally not an odd function. The absolute value transformation destroys the odd symmetry unless f(x) = 0 for all x.
x-intercepts: The x-intercepts of y = |f(x)| are the same as the x-intercepts of y = f(x). This is because |f(x)| = 0 if and only if f(x) = 0.
Continuity: If f(x) is continuous, then |f(x)| is also continuous. However, even if f(x) is differentiable, |f(x)| might not be differentiable at points where f(x) = 0. At these points, the graph of |f(x)| often has a sharp corner or cusp.

Common Mistakes and How to Avoid Them

Incorrectly Reflecting the Entire Graph: A common mistake is to reflect the entire graph of y = f(x) across the x-axis, even the portions that are already above the x-axis. Remember to only reflect the parts where f(x) < 0.
Forgetting to Keep the x-intercepts the Same: The x-intercepts are invariant under the absolute value transformation. Make sure the graph of y = |f(x)| still crosses the x-axis at the same points as the graph of y = f(x).
Misinterpreting the Absolute Value: Remember that the absolute value makes the y-value positive, not the x-value. The reflection is always across the x-axis (changing the sign of the y-value), not the y-axis.
Assuming Differentiability: Be aware that the graph of y = |f(x)| might have sharp corners at points where f(x) = 0, even if f(x) is differentiable. This means that |f(x)| is not differentiable at those points.

Applications of Absolute Value Transformations

Understanding absolute value transformations is useful in various contexts:

Solving Equations and Inequalities: Absolute value transformations are used to solve equations and inequalities involving absolute values. For example, to solve |x - 3| = 5, we consider two cases: x - 3 = 5 and x - 3 = -5.
Calculus: Absolute value functions appear in calculus problems, especially when dealing with limits, continuity, and differentiability. Understanding how the absolute value affects these properties is essential.
Signal Processing: In signal processing, absolute value transformations are used to rectify signals (i.e., convert negative values to positive values).
Physics: Absolute values are used to represent magnitudes of physical quantities, such as speed (the absolute value of velocity).

Beyond y = |f(x)|: Other Absolute Value Transformations

While we've focused on y = |f(x)|, it's worth noting that there are other ways to use absolute values in function transformations. For example:

y = f(|x|): This transformation replaces x with |x| in the original function. The effect is that the graph for x ≥ 0 is mirrored across the y-axis to create the graph for x < 0. This results in an even function, regardless of whether the original f(x) was even or odd.
|y| = f(x): This transformation is less common but involves taking the absolute value of the y-variable. To graph this, you would first graph y = f(x), then reflect the portion of the graph above the x-axis across the x-axis. The resulting graph will be symmetric about the x-axis.

Conclusion

Graphing y = |f(x)| from y = f(x) is a powerful and fundamental technique in understanding function transformations. By understanding the effect of the absolute value on the y-values of a function, you can quickly and accurately sketch the transformed graph. Remember to identify the regions where f(x) < 0 and reflect those portions across the x-axis, leaving the non-negative regions unchanged. With practice, you'll be able to visualize these transformations effortlessly and apply them to a wide range of mathematical problems. This skill will not only improve your understanding of functions but also enhance your problem-solving abilities in mathematics and related fields. The ability to visualize transformations is key to unlocking deeper understanding and intuition in mathematics.