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Ch. 7 - Transcendental Functions
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 7, Problem 7.1.43a

In Exercises 41–44:
a. Find f⁻¹(x).


43. f(x) = 5 − 4x, a = 1/2

Verified step by step guidance
1
Start by writing the function given: \(f(x) = 5 - 4x\).
To find the inverse function \(f^{-1}(x)\), replace \(f(x)\) with \(y\): \(y = 5 - 4x\).
Swap the variables \(x\) and \(y\) to reflect the inverse relationship: \(x = 5 - 4y\).
Solve this equation for \(y\) to express \(y\) in terms of \(x\): subtract 5 from both sides to get \(x - 5 = -4y\), then divide both sides by \(-4\) to isolate \(y\).
Write the inverse function as \(f^{-1}(x) = \frac{5 - x}{4}\) (after simplifying the expression).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Inverse Functions

An inverse function reverses the effect of the original function, swapping inputs and outputs. If f(x) maps x to y, then f⁻¹(x) maps y back to x. Finding the inverse involves solving the equation y = f(x) for x in terms of y.
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Solving Linear Equations

Since f(x) = 5 − 4x is linear, finding its inverse requires isolating x in the equation y = 5 − 4x. This involves algebraic manipulation such as adding, subtracting, multiplying, or dividing both sides to solve for x.
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Domain and Range Considerations

When finding an inverse, it is important to consider the domain and range of the original function and its inverse. The value a = 1/2 may specify a particular input or output to check, ensuring the inverse function is valid at that point.
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