Find the Inverse (x+8)/5

$\frac{x + 8}{5}$

Step 1

Interchange the variables.

$x = \frac{y + 8}{5}$

Step 2

Solve for $y$ .

Rewrite the equation as $\frac{y + 8}{5} = x$ .

$\frac{y + 8}{5} = x$

Multiply both sides of the equation by $5$ .

$5 \frac{y + 8}{5} = 5 x$

Simplify the left side.

Cancel the common factor of $5$ .

Cancel the common factor.

$5 \frac{y + 8}{5} = 5 x$

Rewrite the expression.

$y + 8 = 5 x$

Subtract $8$ from both sides of the equation.

$y = 5 x - 8$

Step 3

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

$f^{- 1} (x) = 5 x - 8$

Step 4

Verify if $f^{- 1} (x) = 5 x - 8$ is the inverse of $f (x) = \frac{x + 8}{5}$ .

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 $f^{- 1} (\frac{x + 8}{5})$ by substituting in the value of $f$ into $f^{- 1}$ .

$f^{- 1} (\frac{x + 8}{5}) = 5 (\frac{x + 8}{5}) - 8$

Cancel the common factor of $5$ .

Cancel the common factor.

$f^{- 1} (\frac{x + 8}{5}) = 5 (\frac{x + 8}{5}) - 8$

Rewrite the expression.

$f^{- 1} (\frac{x + 8}{5}) = x + 8 - 8$

Combine the opposite terms in $x + 8 - 8$ .

Subtract $8$ from $8$ .

$f^{- 1} (\frac{x + 8}{5}) = x + 0$

Add $x$ and $0$ .

$f^{- 1} (\frac{x + 8}{5}) = x$

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

Set up the composite result function.

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

Evaluate $f (5 x - 8)$ by substituting in the value of $f^{- 1}$ into $f$ .

$f (5 x - 8) = \frac{(5 x - 8) + 8}{5}$

Simplify the numerator.

Add $- 8$ and $8$ .

$f (5 x - 8) = \frac{5 x + 0}{5}$

Add $5 x$ and $0$ .

$f (5 x - 8) = \frac{5 x}{5}$

Cancel the common factor of $5$ .

Cancel the common factor.

$f (5 x - 8) = \frac{5 x}{5}$

Divide $x$ by $1$ .

$f (5 x - 8) = x$

Since $f^{- 1} (f (x)) = x$ and $f (f^{- 1} (x)) = x$ , then $f^{- 1} (x) = 5 x - 8$ is the inverse of $f (x) = \frac{x + 8}{5}$ .

$f^{- 1} (x) = 5 x - 8$

Find the Inverse (x+8)/5

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