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Precalculus Chapter 5: Inverses, Exponentials, and Logarithms – Guided Study

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Q1. Find an equation of the inverse relation for .

Background

Topic: Inverse Functions

This question tests your ability to find the inverse of a linear function by switching the roles of and and solving for $y$.

Key Terms and Formulas:

  • Inverse function: If is a function, its inverse undoes the action of $f(x)$.

  • To find the inverse, swap and and solve for $y$.

Step-by-Step Guidance

  1. Start with the original equation: .

  2. Switch and to get .

  3. Solve this new equation for by isolating $y$ on one side.

  4. Once you have by itself, write the inverse relation as

Try solving on your own before revealing the answer!

Final Answer: →

We swapped and and solved for $y$ to find the inverse relation.

Q2. Find an equation of the inverse relation for .

Background

Topic: Inverse Relations (Nonlinear)

This question asks you to find the inverse of a relation involving both and in a nonlinear way.

Key Terms and Formulas:

  • Inverse relation: Swap and and solve for $y$.

  • Be careful with exponents and algebraic manipulation.

Step-by-Step Guidance

  1. Start with the given equation: .

  2. Switch and to get .

  3. Solve for in terms of by isolating $y$.

  4. Express the inverse relation as

Try solving on your own before revealing the answer!

Final Answer: →

After swapping and solving, you get the inverse relation in terms of .

Q3. Graph as a solid line. Graph its inverse as a dashed line by reflecting across .

Background

Topic: Graphing Functions and Their Inverses

This question tests your understanding of how to graph a function and its inverse, and how the inverse is a reflection across the line .

Key Terms and Formulas:

  • Inverse graph: The graph of the inverse is a reflection of the original graph across the line .

  • To graph the inverse, swap the and coordinates of points on the original graph.

Step-by-Step Guidance

  1. Plot the graph of as a solid curve.

  2. Draw the line as a reference (usually a dashed diagonal line).

  3. To graph the inverse, reflect each point on the original graph to .

  4. Sketch the reflected (inverse) curve as a dashed line.

Try sketching the graphs before revealing the answer!

Final Answer:

The graph of is a parabola shifted up 3 units. Its inverse is not a function (unless you restrict the domain), and is the reflection of the parabola across .

Q4. Find the inverse of the function .

Background

Topic: Inverse Functions (Linear)

This question asks you to find the inverse of a simple linear function.

Key Terms and Formulas:

  • Inverse function: undoes the action of .

  • To find the inverse, swap and and solve for $y$.

Step-by-Step Guidance

  1. Write .

  2. Swap and to get .

  3. Solve for by dividing both sides by 7.

  4. Write the inverse function as

Try solving on your own before revealing the answer!

Final Answer:

The inverse function undoes the multiplication by 7 by dividing by 7.

Q5. Find the inverse of the function .

Background

Topic: Inverse Functions (Linear with Fractional Coefficient)

This question tests your ability to find the inverse of a linear function with a fractional coefficient.

Key Terms and Formulas:

  • Inverse function: Swap and and solve for $y$.

  • Be careful with fractions when isolating .

Step-by-Step Guidance

  1. Write .

  2. Swap and to get .

  3. Subtract 6 from both sides to isolate the term with .

  4. Multiply both sides by 4 to solve for .

  5. Write the inverse function as

Try solving on your own before revealing the answer!

Final Answer:

We isolated and solved for the inverse function.

Q6. For and , use composition to show that is the inverse of .

Background

Topic: Verifying Inverses Using Composition

This question asks you to use function composition to verify that two functions are inverses.

Key Terms and Formulas:

  • Composition: and

  • If and are true inverses, both compositions should return .

Step-by-Step Guidance

  1. Compute by substituting into .

  2. Simplify the expression to see if it equals .

  3. Compute by substituting into .

  4. Simplify this expression as well.

  5. If both simplify to , the functions are inverses.

Try working through the compositions before revealing the answer!

Final Answer:

Both and simplify to , confirming that the functions are inverses.

Q7. For and , use composition to show that is the inverse of .

Background

Topic: Verifying Inverses Using Composition (Rational Functions)

This question asks you to verify that two rational functions are inverses by using composition.

Key Terms and Formulas:

  • Composition: and

  • If both compositions return , the functions are inverses.

Step-by-Step Guidance

  1. Compute by plugging into .

  2. Simplify the resulting expression step by step.

  3. Compute by plugging into .

  4. Simplify this expression as well.

  5. Check if both compositions simplify to .

Try working through the algebra before revealing the answer!

Final Answer:

Both compositions simplify to , confirming that the functions are inverses.

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