Find the Inverse (3x)/(x-7)

$\frac{3 x}{x - 7}$

Step 1

Interchange the variables.

$x = \frac{3 y}{y - 7}$

Step 2

Solve for $y$ .

Multiply the equation by $y - 7$ .

$(y - 7) (x) = (\frac{3 y}{y - 7}) (y - 7)$

Simplify the left side.

Apply the distributive property.

$y x - 7 x = (\frac{3 y}{y - 7}) (y - 7)$

Simplify the right side.

Cancel the common factor of $y - 7$ .

Cancel the common factor.

$y x - 7 x = \frac{3 y}{y - 7} (y - 7)$

Rewrite the expression.

$y x - 7 x = 3 y$

Solve for $y$ .

Subtract $3 y$ from both sides of the equation.

$y x - 7 x - 3 y = 0$

Add $7 x$ to both sides of the equation.

$y x - 3 y = 7 x$

Factor $y$ out of $y x - 3 y$ .

Factor $y$ out of $y x$ .

$y (x) - 3 y = 7 x$

Factor $y$ out of $- 3 y$ .

$y (x) + y \cdot - 3 = 7 x$

Factor $y$ out of $y (x) + y \cdot - 3$ .

$y (x - 3) = 7 x$

Divide each term in $y (x - 3) = 7 x$ by $x - 3$ and simplify.

Divide each term in $y (x - 3) = 7 x$ by $x - 3$ .

$\frac{y (x - 3)}{x - 3} = \frac{7 x}{x - 3}$

Simplify the left side.

Cancel the common factor of $x - 3$ .

Cancel the common factor.

$\frac{y (x - 3)}{x - 3} = \frac{7 x}{x - 3}$

Divide $y$ by $1$ .

$y = \frac{7 x}{x - 3}$

Step 3

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

$f^{- 1} (x) = \frac{7 x}{x - 3}$

Step 4

Verify if $f^{- 1} (x) = \frac{7 x}{x - 3}$ is the inverse of $f (x) = \frac{3 x}{x - 7}$ .

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 $f^{- 1} (\frac{3 x}{x - 7})$ by substituting in the value of $f$ into $f^{- 1}$ .

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{7 (\frac{3 x}{x - 7})}{(\frac{3 x}{x - 7}) - 3}$

Combine $7$ and $\frac{3 x}{x - 7}$ .

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{\frac{7 (3 x)}{x - 7}}{\frac{3 x}{x - 7} - 3}$

Simplify the denominator.

To write $- 3$ as a fraction with a common denominator, multiply by $\frac{x - 7}{x - 7}$ .

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{\frac{7 (3 x)}{x - 7}}{\frac{3 x}{x - 7} - 3 \cdot \frac{x - 7}{x - 7}}$

Combine $- 3$ and $\frac{x - 7}{x - 7}$ .

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{\frac{7 (3 x)}{x - 7}}{\frac{3 x}{x - 7} + \frac{- 3 (x - 7)}{x - 7}}$

Combine the numerators over the common denominator.

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{\frac{7 (3 x)}{x - 7}}{\frac{3 x - 3 (x - 7)}{x - 7}}$

Rewrite $\frac{3 x - 3 (x - 7)}{x - 7}$ in a factored form.

Factor $3$ out of $3 x - 3 (x - 7)$ .

Factor $3$ out of $3 x$ .

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{\frac{7 (3 x)}{x - 7}}{\frac{3 (x) - 3 (x - 7)}{x - 7}}$

Factor $3$ out of $- 3 (x - 7)$ .

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{\frac{7 (3 x)}{x - 7}}{\frac{3 (x) + 3 (- (x - 7))}{x - 7}}$

Factor $3$ out of $3 (x) + 3 (- (x - 7))$ .

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{\frac{7 (3 x)}{x - 7}}{\frac{3 (x - (x - 7))}{x - 7}}$

Apply the distributive property.

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{\frac{7 (3 x)}{x - 7}}{\frac{3 (x - x + 7)}{x - 7}}$

Multiply $- 1$ by $- 7$ .

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{\frac{7 (3 x)}{x - 7}}{\frac{3 (x - x + 7)}{x - 7}}$

Subtract $x$ from $x$ .

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{\frac{7 (3 x)}{x - 7}}{\frac{3 (0 + 7)}{x - 7}}$

Add $0$ and $7$ .

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{\frac{7 (3 x)}{x - 7}}{\frac{3 \cdot 7}{x - 7}}$

Multiply $3$ by $7$ .

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{\frac{7 (3 x)}{x - 7}}{\frac{21}{x - 7}}$

Multiply $7$ by $3$ .

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{\frac{21 x}{x - 7}}{\frac{21}{x - 7}}$

Multiply the numerator by the reciprocal of the denominator.

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{21 x}{x - 7} \cdot \frac{x - 7}{21}$

Cancel the common factor of $21$ .

Factor $21$ out of $21 x$ .

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{21 (x)}{x - 7} \cdot \frac{x - 7}{21}$

Cancel the common factor.

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{21 x}{x - 7} \cdot \frac{x - 7}{21}$

Rewrite the expression.

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{x}{x - 7} \cdot (x - 7)$

Cancel the common factor of $x - 7$ .

Cancel the common factor.

$f^{- 1} (\frac{3 x}{x - 7}) = \frac{x}{x - 7} \cdot (x - 7)$

Rewrite the expression.

$f^{- 1} (\frac{3 x}{x - 7}) = x$

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

Set up the composite result function.

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

Evaluate $f (\frac{7 x}{x - 3})$ by substituting in the value of $f^{- 1}$ into $f$ .

$f (\frac{7 x}{x - 3}) = \frac{3 (\frac{7 x}{x - 3})}{(\frac{7 x}{x - 3}) - 7}$

Combine $3$ and $\frac{7 x}{x - 3}$ .

$f (\frac{7 x}{x - 3}) = \frac{\frac{3 (7 x)}{x - 3}}{\frac{7 x}{x - 3} - 7}$

Simplify the denominator.

To write $- 7$ as a fraction with a common denominator, multiply by $\frac{x - 3}{x - 3}$ .

$f (\frac{7 x}{x - 3}) = \frac{\frac{3 (7 x)}{x - 3}}{\frac{7 x}{x - 3} - 7 \cdot \frac{x - 3}{x - 3}}$

Combine $- 7$ and $\frac{x - 3}{x - 3}$ .

$f (\frac{7 x}{x - 3}) = \frac{\frac{3 (7 x)}{x - 3}}{\frac{7 x}{x - 3} + \frac{- 7 (x - 3)}{x - 3}}$

Combine the numerators over the common denominator.

$f (\frac{7 x}{x - 3}) = \frac{\frac{3 (7 x)}{x - 3}}{\frac{7 x - 7 (x - 3)}{x - 3}}$

Rewrite $\frac{7 x - 7 (x - 3)}{x - 3}$ in a factored form.

Factor $7$ out of $7 x - 7 (x - 3)$ .

Factor $7$ out of $7 x$ .

$f (\frac{7 x}{x - 3}) = \frac{\frac{3 (7 x)}{x - 3}}{\frac{7 (x) - 7 (x - 3)}{x - 3}}$

Factor $7$ out of $- 7 (x - 3)$ .

$f (\frac{7 x}{x - 3}) = \frac{\frac{3 (7 x)}{x - 3}}{\frac{7 (x) + 7 (- (x - 3))}{x - 3}}$

Factor $7$ out of $7 (x) + 7 (- (x - 3))$ .

$f (\frac{7 x}{x - 3}) = \frac{\frac{3 (7 x)}{x - 3}}{\frac{7 (x - (x - 3))}{x - 3}}$

Apply the distributive property.

$f (\frac{7 x}{x - 3}) = \frac{\frac{3 (7 x)}{x - 3}}{\frac{7 (x - x + 3)}{x - 3}}$

Multiply $- 1$ by $- 3$ .

$f (\frac{7 x}{x - 3}) = \frac{\frac{3 (7 x)}{x - 3}}{\frac{7 (x - x + 3)}{x - 3}}$

Subtract $x$ from $x$ .

$f (\frac{7 x}{x - 3}) = \frac{\frac{3 (7 x)}{x - 3}}{\frac{7 (0 + 3)}{x - 3}}$

Add $0$ and $3$ .

$f (\frac{7 x}{x - 3}) = \frac{\frac{3 (7 x)}{x - 3}}{\frac{7 \cdot 3}{x - 3}}$

Multiply $7$ by $3$ .

$f (\frac{7 x}{x - 3}) = \frac{\frac{3 (7 x)}{x - 3}}{\frac{21}{x - 3}}$

Multiply $3$ by $7$ .

$f (\frac{7 x}{x - 3}) = \frac{\frac{21 x}{x - 3}}{\frac{21}{x - 3}}$

Multiply the numerator by the reciprocal of the denominator.

$f (\frac{7 x}{x - 3}) = \frac{21 x}{x - 3} \cdot \frac{x - 3}{21}$

Cancel the common factor of $21$ .

Factor $21$ out of $21 x$ .

$f (\frac{7 x}{x - 3}) = \frac{21 (x)}{x - 3} \cdot \frac{x - 3}{21}$

Cancel the common factor.

$f (\frac{7 x}{x - 3}) = \frac{21 x}{x - 3} \cdot \frac{x - 3}{21}$

Rewrite the expression.

$f (\frac{7 x}{x - 3}) = \frac{x}{x - 3} \cdot (x - 3)$

Cancel the common factor of $x - 3$ .

Cancel the common factor.

$f (\frac{7 x}{x - 3}) = \frac{x}{x - 3} \cdot (x - 3)$

Rewrite the expression.

$f (\frac{7 x}{x - 3}) = x$

Since $f^{- 1} (f (x)) = x$ and $f (f^{- 1} (x)) = x$ , then $f^{- 1} (x) = \frac{7 x}{x - 3}$ is the inverse of $f (x) = \frac{3 x}{x - 7}$ .

$f^{- 1} (x) = \frac{7 x}{x - 3}$

Find the Inverse (3x)/(x-7)

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