Use completing the square to solve for x in the equation (x-12)(x+4)=9. a. x = –1 or 15 b. x = 1 or 7 c. x=4+√41 d. x=4+√73

For a quadratic of the form , we can solve by completing the square.

First, we must expand the expression and convert it to the form above.



Completing the square is like forcing a quadratic to be factored like a perfect square trinomial. To do so, we add the square of half of the coefficient b, , to both sides of the equation.



We then factor like a perfect square trinomial and simplify.