Subtract from both sides of the equation.

To create a trinomial square on the left side of the equation, find a value that is equal to the square of half of .

Add the term to each side of the equation.

Raise to the power of .

Simplify .

Raise to the power of .

Add and .

Factor the perfect trinomial square into .

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 .

Remove parentheses.

Subtract from both sides of the equation.

The result can be shown in multiple forms.

Exact Form:

Decimal Form:

Solve by Completing the Square x^2+12x+21=0