Precalculus Examples

$x - 4$

Step 1

Interchange the variables.

$x = y - 4$

Step 2

Solve for $y$ .

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Step 2.1

Rewrite the equation as $y - 4 = x$ .

$y - 4 = x$

Step 2.2

Add $4$ to both sides of the equation.

$y = x + 4$

Step 3

Replace $y$ with $f^{- 1} (x)$ to show the final answer.

$f^{- 1} (x) = x + 4$

Step 4

Verify if $f^{- 1} (x) = x + 4$ is the inverse of $f (x) = x - 4$ .

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Step 4.1

To verify the inverse, check if $f^{- 1} (f (x)) = x$ and $f (f^{- 1} (x)) = x$ .

Step 4.2

Evaluate $f^{- 1} (f (x))$ .

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Step 4.2.1

Set up the composite result function.

$f^{- 1} (f (x))$

Step 4.2.2

Evaluate $f^{- 1} (x - 4)$ by substituting in the value of $f$ into $f^{- 1}$ .

$f^{- 1} (x - 4) = (x - 4) + 4$

Step 4.2.3

Combine the opposite terms in $(x - 4) + 4$ .

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Step 4.2.3.1

Add $- 4$ and $4$ .

$f^{- 1} (x - 4) = x + 0$

Step 4.2.3.2

Add $x$ and $0$ .

$f^{- 1} (x - 4) = x$

Step 4.3

Evaluate $f (f^{- 1} (x))$ .

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Step 4.3.1

Set up the composite result function.

$f (f^{- 1} (x))$

Step 4.3.2

Evaluate $f (x + 4)$ by substituting in the value of $f^{- 1}$ into $f$ .

$f (x + 4) = (x + 4) - 4$

Step 4.3.3

Combine the opposite terms in $(x + 4) - 4$ .

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Step 4.3.3.1

Subtract $4$ from $4$ .

$f (x + 4) = x + 0$

Step 4.3.3.2

Add $x$ and $0$ .

$f (x + 4) = x$

Step 4.4

Since $f^{- 1} (f (x)) = x$ and $f (f^{- 1} (x)) = x$ , then $f^{- 1} (x) = x + 4$ is the inverse of $f (x) = x - 4$ .

$f^{- 1} (x) = x + 4$