Use completing the square to solve for x in the equation (x+7)(x-9)=25 x = –4 or 6 x = –2 or 14 x = 1 ± sqrt(89) x = 1 ± sqrt(87)

First, we need to expand the left hand side expression:



The quadratic and linear terms  are 'produced' from the expansion of the binomial  which is .

Thus, we can write  as , which is equal to 
                               

     
Thus, the equation is . Adding 64 to both sides, we have:
                                        .

 This means that x-1 is either  or .

Finally, we see that x is either or .

 x = 1 ± sqrt(89)