Find the Inverse f(x)=(7x+18)/2

$f (x) = \frac{7 x + 18}{2}$

Step 1

Write $f (x) = \frac{7 x + 18}{2}$ as an equation.

$y = \frac{7 x + 18}{2}$

Step 2

Interchange the variables.

$x = \frac{7 y + 18}{2}$

Step 3

Solve for $y$ .

Rewrite the equation as $\frac{7 y + 18}{2} = x$ .

$\frac{7 y + 18}{2} = x$

Multiply both sides by $2$ .

$\frac{7 y + 18}{2} \cdot 2 = x \cdot 2$

Simplify.

Simplify the left side.

Cancel the common factor of $2$ .

Cancel the common factor.

$\frac{7 y + 18}{2} \cdot 2 = x \cdot 2$

Rewrite the expression.

$7 y + 18 = x \cdot 2$

Simplify the right side.

Move $2$ to the left of $x$ .

$7 y + 18 = 2 x$

Solve for $y$ .

Subtract $18$ from both sides of the equation.

$7 y = 2 x - 18$

Divide each term in $7 y = 2 x - 18$ by $7$ and simplify.

Divide each term in $7 y = 2 x - 18$ by $7$ .

$\frac{7 y}{7} = \frac{2 x}{7} + \frac{- 18}{7}$

Simplify the left side.

Cancel the common factor of $7$ .

Cancel the common factor.

$\frac{7 y}{7} = \frac{2 x}{7} + \frac{- 18}{7}$

Divide $y$ by $1$ .

$y = \frac{2 x}{7} + \frac{- 18}{7}$

Simplify the right side.

Move the negative in front of the fraction.

$y = \frac{2 x}{7} - \frac{18}{7}$

Step 4

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

$f^{- 1} (x) = \frac{2 x}{7} - \frac{18}{7}$

Step 5

Verify if $f^{- 1} (x) = \frac{2 x}{7} - \frac{18}{7}$ is the inverse of $f (x) = \frac{7 x + 18}{2}$ .

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 $f^{- 1} (\frac{7 x + 18}{2})$ by substituting in the value of $f$ into $f^{- 1}$ .

$f^{- 1} (\frac{7 x + 18}{2}) = \frac{2 (\frac{7 x + 18}{2})}{7} - \frac{18}{7}$

Combine the numerators over the common denominator.

$f^{- 1} (\frac{7 x + 18}{2}) = \frac{2 (\frac{7 x + 18}{2}) - 18}{7}$

Cancel the common factor of $2$ .

Cancel the common factor.

$f^{- 1} (\frac{7 x + 18}{2}) = \frac{2 (\frac{7 x + 18}{2}) - 18}{7}$

Rewrite the expression.

$f^{- 1} (\frac{7 x + 18}{2}) = \frac{7 x + 18 - 18}{7}$

Combine the opposite terms in $7 x + 18 - 18$ .

Subtract $18$ from $18$ .

$f^{- 1} (\frac{7 x + 18}{2}) = \frac{7 x + 0}{7}$

Add $7 x$ and $0$ .

$f^{- 1} (\frac{7 x + 18}{2}) = \frac{7 x}{7}$

Cancel the common factor of $7$ .

Cancel the common factor.

$f^{- 1} (\frac{7 x + 18}{2}) = \frac{7 x}{7}$

Divide $x$ by $1$ .

$f^{- 1} (\frac{7 x + 18}{2}) = x$

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

Set up the composite result function.

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

Evaluate $f (\frac{2 x}{7} - \frac{18}{7})$ by substituting in the value of $f^{- 1}$ into $f$ .

$f (\frac{2 x}{7} - \frac{18}{7}) = \frac{7 (\frac{2 x}{7} - \frac{18}{7}) + 18}{2}$

Simplify the numerator.

Apply the distributive property.

$f (\frac{2 x}{7} - \frac{18}{7}) = \frac{7 (\frac{2 x}{7}) + 7 (- \frac{18}{7}) + 18}{2}$

Cancel the common factor of $7$ .

Cancel the common factor.

$f (\frac{2 x}{7} - \frac{18}{7}) = \frac{7 (\frac{2 x}{7}) + 7 (- \frac{18}{7}) + 18}{2}$

Rewrite the expression.

$f (\frac{2 x}{7} - \frac{18}{7}) = \frac{2 x + 7 (- \frac{18}{7}) + 18}{2}$

Cancel the common factor of $7$ .

Move the leading negative in $- \frac{18}{7}$ into the numerator.

$f (\frac{2 x}{7} - \frac{18}{7}) = \frac{2 x + 7 (\frac{- 18}{7}) + 18}{2}$

Cancel the common factor.

$f (\frac{2 x}{7} - \frac{18}{7}) = \frac{2 x + 7 (\frac{- 18}{7}) + 18}{2}$

Rewrite the expression.

$f (\frac{2 x}{7} - \frac{18}{7}) = \frac{2 x - 18 + 18}{2}$

Add $- 18$ and $18$ .

$f (\frac{2 x}{7} - \frac{18}{7}) = \frac{2 x + 0}{2}$

Add $2 x$ and $0$ .

$f (\frac{2 x}{7} - \frac{18}{7}) = \frac{2 x}{2}$

Cancel the common factor of $2$ .

Cancel the common factor.

$f (\frac{2 x}{7} - \frac{18}{7}) = \frac{2 x}{2}$

Divide $x$ by $1$ .

$f (\frac{2 x}{7} - \frac{18}{7}) = x$

Since $f^{- 1} (f (x)) = x$ and $f (f^{- 1} (x)) = x$ , then $f^{- 1} (x) = \frac{2 x}{7} - \frac{18}{7}$ is the inverse of $f (x) = \frac{7 x + 18}{2}$ .

$f^{- 1} (x) = \frac{2 x}{7} - \frac{18}{7}$

Find the Inverse f(x)=(7x+18)/2

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