Interchange the variables.

Rewrite the equation as .

Move to the left side of the equation by subtracting it from both sides.

Use the quadratic formula to find the solutions.

Substitute the values , , and into the quadratic formula and solve for .

Simplify.

Simplify the numerator.

Raise to the power of .

Multiply by .

Multiply by .

Factor out of .

Factor out of .

Factor out of .

Rewrite as .

Rewrite as .

Rewrite as .

Pull terms out from under the radical.

Raise to the power of .

Multiply by .

Simplify .

Simplify the expression to solve for the portion of the .

Simplify the numerator.

Raise to the power of .

Multiply by .

Multiply by .

Factor out of .

Factor out of .

Factor out of .

Rewrite as .

Rewrite as .

Rewrite as .

Pull terms out from under the radical.

Raise to the power of .

Multiply by .

Simplify .

Change the to .

Simplify the expression to solve for the portion of the .

Simplify the numerator.

Raise to the power of .

Multiply by .

Multiply by .

Factor out of .

Factor out of .

Factor out of .

Rewrite as .

Rewrite as .

Rewrite as .

Pull terms out from under the radical.

Raise to the power of .

Multiply by .

Simplify .

Change the to .

The final answer is the combination of both solutions.

Replace the with to show the final answer.

Set up the composite result function.

Evaluate by substituting in the value of into .

Remove parentheses.

Simplify each term.

Factor using the perfect square rule.

Rearrange terms.

Rewrite as .

Check the middle term by multiplying and compare this result with the middle term in the original expression.

Simplify.

Factor using the perfect square trinomial rule , where and .

Pull terms out from under the radical, assuming positive real numbers.

Add and .

Since , is the inverse of .

Find the Inverse y=x^2-18x