Find the Inverse 8x+9

$8 x + 9$

Step 1

Interchange the variables.

$x = 8 y + 9$

Step 2

Solve for $y$ .

Rewrite the equation as $8 y + 9 = x$ .

$8 y + 9 = x$

Subtract $9$ from both sides of the equation.

$8 y = x - 9$

Divide each term in $8 y = x - 9$ by $8$ and simplify.

Divide each term in $8 y = x - 9$ by $8$ .

$\frac{8 y}{8} = \frac{x}{8} + \frac{- 9}{8}$

Simplify the left side.

Cancel the common factor of $8$ .

Cancel the common factor.

$\frac{8 y}{8} = \frac{x}{8} + \frac{- 9}{8}$

Divide $y$ by $1$ .

$y = \frac{x}{8} + \frac{- 9}{8}$

Simplify the right side.

Move the negative in front of the fraction.

$y = \frac{x}{8} - \frac{9}{8}$

Step 3

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

$f^{- 1} (x) = \frac{x}{8} - \frac{9}{8}$

Step 4

Verify if $f^{- 1} (x) = \frac{x}{8} - \frac{9}{8}$ is the inverse of $f (x) = 8 x + 9$ .

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 $f^{- 1} (8 x + 9)$ by substituting in the value of $f$ into $f^{- 1}$ .

$f^{- 1} (8 x + 9) = \frac{8 x + 9}{8} - \frac{9}{8}$

Combine the numerators over the common denominator.

$f^{- 1} (8 x + 9) = \frac{8 x + 9 - 9}{8}$

Combine the opposite terms in $8 x + 9 - 9$ .

Subtract $9$ from $9$ .

$f^{- 1} (8 x + 9) = \frac{8 x + 0}{8}$

Add $8 x$ and $0$ .

$f^{- 1} (8 x + 9) = \frac{8 x}{8}$

Cancel the common factor of $8$ .

Cancel the common factor.

$f^{- 1} (8 x + 9) = \frac{8 x}{8}$

Divide $x$ by $1$ .

$f^{- 1} (8 x + 9) = x$

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

Set up the composite result function.

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

Evaluate $f (\frac{x}{8} - \frac{9}{8})$ by substituting in the value of $f^{- 1}$ into $f$ .

$f (\frac{x}{8} - \frac{9}{8}) = 8 (\frac{x}{8} - \frac{9}{8}) + 9$

Simplify each term.

Apply the distributive property.

$f (\frac{x}{8} - \frac{9}{8}) = 8 (\frac{x}{8}) + 8 (- \frac{9}{8}) + 9$

Cancel the common factor of $8$ .

Cancel the common factor.

$f (\frac{x}{8} - \frac{9}{8}) = 8 (\frac{x}{8}) + 8 (- \frac{9}{8}) + 9$

Rewrite the expression.

$f (\frac{x}{8} - \frac{9}{8}) = x + 8 (- \frac{9}{8}) + 9$

Cancel the common factor of $8$ .

Move the leading negative in $- \frac{9}{8}$ into the numerator.

$f (\frac{x}{8} - \frac{9}{8}) = x + 8 (\frac{- 9}{8}) + 9$

Cancel the common factor.

$f (\frac{x}{8} - \frac{9}{8}) = x + 8 (\frac{- 9}{8}) + 9$

Rewrite the expression.

$f (\frac{x}{8} - \frac{9}{8}) = x - 9 + 9$

Combine the opposite terms in $x - 9 + 9$ .

Add $- 9$ and $9$ .

$f (\frac{x}{8} - \frac{9}{8}) = x + 0$

Add $x$ and $0$ .

$f (\frac{x}{8} - \frac{9}{8}) = x$

Since $f^{- 1} (f (x)) = x$ and $f (f^{- 1} (x)) = x$ , then $f^{- 1} (x) = \frac{x}{8} - \frac{9}{8}$ is the inverse of $f (x) = 8 x + 9$ .

$f^{- 1} (x) = \frac{x}{8} - \frac{9}{8}$

Find the Inverse 8x+9

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