Find the Inverse y=4x

$y = 4 x$

Step 1

Interchange the variables.

$x = 4 y$

Step 2

Solve for $y$ .

Rewrite the equation as $4 y = x$ .

$4 y = x$

Divide each term in $4 y = x$ by $4$ and simplify.

Divide each term in $4 y = x$ by $4$ .

$\frac{4 y}{4} = \frac{x}{4}$

Simplify the left side.

Cancel the common factor of $4$ .

Cancel the common factor.

$\frac{4 y}{4} = \frac{x}{4}$

Divide $y$ by $1$ .

$y = \frac{x}{4}$

Step 3

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

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

Step 4

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

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

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

Cancel the common factor of $4$ .

Cancel the common factor.

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

Divide $x$ by $1$ .

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

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

Set up the composite result function.

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

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

$f (\frac{x}{4}) = 4 (\frac{x}{4})$

Cancel the common factor of $4$ .

Cancel the common factor.

$f (\frac{x}{4}) = 4 (\frac{x}{4})$

Rewrite the expression.

$f (\frac{x}{4}) = x$

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

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