Rewrite the equation as .

Subtract from both sides of the equation.

Simplify each term.

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

Multiply by .

Subtract from .

Multiply each term in by .

Multiply .

Multiply by .

Multiply by .

Multiply by .

Take the square root of each side of the equation to set up the solution for

Remove the perfect root factor under the radical to solve for .

First, use the positive value of the to find the first solution.

Add to both sides of the equation.

Next, use the negative value of the to find the second solution.

Add to both sides of the equation.

The complete solution is the result of both the positive and negative portions of the solution.

The result can be shown in multiple forms.

Exact Form:

Decimal Form:

Solve for r 36 = square root of 39^2-(r-6)^2