Find the Inverse y=3x

$y = 3 x$

Step 1

Interchange the variables.

$x = 3 y$

Step 2

Solve for $y$ .

Rewrite the equation as $3 y = x$ .

$3 y = x$

Divide each term in $3 y = x$ by $3$ and simplify.

Divide each term in $3 y = x$ by $3$ .

$\frac{3 y}{3} = \frac{x}{3}$

Simplify the left side.

Cancel the common factor of $3$ .

Cancel the common factor.

$\frac{3 y}{3} = \frac{x}{3}$

Divide $y$ by $1$ .

$y = \frac{x}{3}$

Step 3

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

$f^{- 1} (x) = \frac{x}{3}$

Step 4

Verify if $f^{- 1} (x) = \frac{x}{3}$ is the inverse of $f (x) = 3 x$ .

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 $f^{- 1} (3 x)$ by substituting in the value of $f$ into $f^{- 1}$ .

$f^{- 1} (3 x) = \frac{3 x}{3}$

Cancel the common factor of $3$ .

Cancel the common factor.

$f^{- 1} (3 x) = \frac{3 x}{3}$

Divide $x$ by $1$ .

$f^{- 1} (3 x) = x$

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

Set up the composite result function.

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

Evaluate $f (\frac{x}{3})$ by substituting in the value of $f^{- 1}$ into $f$ .

$f (\frac{x}{3}) = 3 (\frac{x}{3})$

Cancel the common factor of $3$ .

Cancel the common factor.

$f (\frac{x}{3}) = 3 (\frac{x}{3})$

Rewrite the expression.

$f (\frac{x}{3}) = x$

Since $f^{- 1} (f (x)) = x$ and $f (f^{- 1} (x)) = x$ , then $f^{- 1} (x) = \frac{x}{3}$ is the inverse of $f (x) = 3 x$ .

$f^{- 1} (x) = \frac{x}{3}$