Which Equation is the Inverse of Y = 100 – X2?

To find the inverse of a function, you typically switch the roles of the dependent variable (y) and the independent variable (x) and solve for the new dependent variable. In this case, you have the function:

y = 100 – x^2

To find its inverse, you switch y and x:

x = 100 – y^2

Now, you’ll solve for y:

x = 100 – y^2

First, subtract x from both sides:

• x = -y^2

Next, multiply both sides by -1 to isolate y^2:

x = y^2

Now, take the square root of both sides. Remember to consider both the positive and negative square roots since a square root can be either positive or negative:

√x = ±√(y^2)

This simplifies to:

√x = ±y

Now, solve for y:

y = ±√x

So, the equation that represents the inverse of y = 100 – x^2 is:

y = ±√x

In this inverse function, for each value of x, there are two possible values of y, one positive and one negative. This reflects the fact that the original function is not one-to-one, meaning that multiple values of x can correspond to the same value of y.

Inverse functions are essential in mathematics and various fields, as they allow us to “reverse” the effect of a given function. When you have a function, like y = 100 – x^2, its inverse undoes the operation of the original function. In this case, the original function represents a downward-opening parabola, with its vertex at the point (0, 100). This parabola describes a relationship between x and y, where y decreases as x increases.

Now, when we find the inverse of this function, we obtain y = ±√x. This inverse function has a fascinating property that stems from the original function’s behavior. Let’s dive into a few key points:

1. Positive and Negative Solutions: The presence of the ± symbol in the inverse function indicates that for each value of x, there are two corresponding values of y. One value of y is the positive square root of x, and the other is the negative square root of x. This reflects the symmetry of the original function, where for every point (x, y) on the graph, there’s a corresponding point (x, -y) on the other side of the x-axis.
2. Reflection Across the X-Axis: The inverse function y = ±√x represents a reflection of the original function y = 100 – x^2 across the x-axis. In other words, if you were to take the graph of the original function and flip it over the x-axis, you would obtain the graph of the inverse function. This is a common property of functions and their inverses.
3. Multivalued Function: The inverse function y = ±√x is an example of a multivalued function. A multivalued function has more than one output for a given input. In this case, each input x has two possible outputs: one positive and one negative. Multivalued functions are not always considered “functions” in the strict mathematical sense, but they are still valuable mathematical objects.
4. Practical Applications: In some practical scenarios, the multivalued nature of the inverse function can have significance. For example, in physics, when dealing with motion in both the upward and downward directions, the ± symbol can represent two possible solutions to a problem. Similarly, in electrical engineering, when dealing with alternating current (AC) signals, the ± symbol can represent the positive and negative phases of the waveform.

In summary, the inverse of y = 100 – x^2, which is represented as y = ±√x, is a multivalued function that reflects the original function across the x-axis. It captures the symmetry and dual nature of the original function, where each value of x corresponds to both a positive and a negative value of y. Understanding the ± symbol in the context of inverse functions helps us appreciate the complexity and richness of mathematical relationships and their applications in various fields.

Practical Applications of Inverse Functions:

1. Exponential and Logarithmic Functions: Exponential functions, such as y = 2^x, have inverse logarithmic functions, like y = log2(x). These functions are crucial in various fields, including finance (compound interest calculations), science (population growth), and engineering (signal processing).
2. Trigonometric Functions: Trigonometric functions like sine, cosine, and tangent have their inverse counterparts, arcsin, arccos, and arctan. These functions are essential in fields like physics, engineering, and computer graphics for modeling periodic phenomena, such as waveforms and oscillations.
3. Probability and Statistics: The cumulative distribution function (CDF) of a random variable corresponds to its probability distribution function (PDF). These functions are often used in statistics and probability theory to describe the likelihood of different outcomes in various scenarios.
4. Electrical Engineering: In electrical engineering, the concept of impedance and admittance involves complex numbers. The impedance of a circuit element is related to its admittance through complex conjugates, demonstrating the use of inverse functions in analyzing AC circuits.
5. Medical Imaging: In medical imaging, the Radon transform is used to reconstruct images from projections taken at various angles. Its inverse, known as the filtered back projection, is employed to create detailed images from the collected data in techniques like computed tomography (CT) scans.
6. Economics and Finance: In economics, functions like the marginal cost and marginal revenue functions are related through their inverses. Understanding the inverse relationship between these functions is crucial for optimizing production and pricing decisions in business.
7. Cryptography: In the field of cryptography, mathematical functions and their inverses play a fundamental role in ensuring secure communication. For instance, public-key cryptography relies on the difficulty of finding the inverse of a particular mathematical operation.
8. Engineering Control Systems: In control systems engineering, transfer functions and their inverses are used to analyze and design feedback control systems. The inverse of a transfer function is essential for designing controllers that can achieve desired system responses.

The Importance of Inverse Functions in Problem-Solving:

Inverse functions provide a powerful tool for problem-solving and modeling real-world phenomena. They allow us to “undo” operations and find solutions to equations and systems. In many practical situations, understanding the relationship between a function and its inverse is essential for optimizing processes, making informed decisions, and solving complex problems.

Challenges with Inverse Functions:

While inverse functions are invaluable, they are not always straightforward to find or use. In some cases, a function may not have an easily expressible inverse. Additionally, certain practical problems may have multiple solutions, leading to multivalued inverse functions, as we explored with the ± symbol earlier.

In conclusion, inverse functions are a fundamental concept in mathematics and have wide-ranging applications in diverse fields. They provide a means of “reversing” mathematical operations and solving real-world problems. Understanding the properties and practical applications of inverse functions enriches our ability to analyze complex systems, make informed decisions, and model the world around us.