Find the Inverse f(x)=x+18

$f (x) = x + 18$

Step 1

Write $f (x) = x + 18$ as an equation.

$y = x + 18$

Step 2

Interchange the variables.

$x = y + 18$

Step 3

Solve for $y$ .

Rewrite the equation as $y + 18 = x$ .

$y + 18 = x$

Subtract $18$ from both sides of the equation.

$y = x - 18$

Step 4

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

$f^{- 1} (x) = x - 18$

Step 5

Verify if $f^{- 1} (x) = x - 18$ is the inverse of $f (x) = x + 18$ .

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

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

Set up the composite result function.

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

Evaluate $f^{- 1} (x + 18)$ by substituting in the value of $f$ into $f^{- 1}$ .

$f^{- 1} (x + 18) = (x + 18) - 18$

Combine the opposite terms in $(x + 18) - 18$ .

Subtract $18$ from $18$ .

$f^{- 1} (x + 18) = x + 0$

Add $x$ and $0$ .

$f^{- 1} (x + 18) = x$

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

Set up the composite result function.

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

Evaluate $f (x - 18)$ by substituting in the value of $f^{- 1}$ into $f$ .

$f (x - 18) = (x - 18) + 18$

Combine the opposite terms in $(x - 18) + 18$ .

Add $- 18$ and $18$ .

$f (x - 18) = x + 0$

Add $x$ and $0$ .

$f (x - 18) = x$

Since $f^{- 1} (f (x)) = x$ and $f (f^{- 1} (x)) = x$ , then $f^{- 1} (x) = x - 18$ is the inverse of $f (x) = x + 18$ .

$f^{- 1} (x) = x - 18$