You can 
put this solution on YOUR website! Factor            x² + 4xy + 4y² - 16
We have to recognize that the first three terms
will factor as a perfect square:
                  x² + 4xy + 4y² - 16
                (x + 2y)(x + 2y) - 16
                       (x + 2y)² - 16
Now this factors again as the difference of two squares
                       (x + 2y)² - 4²
               [(x + 2y) - 4][(x + 2y) + 4]
                 [x + 2y - 4][x + 2y + 4]
                 (x + 2y - 4)(x + 2y + 4)
factor         12(x + 1)² - 17(x + 1) + 6 
Replace (x + 1) by a single letter, say W, then
W = (x + 1)
                   12W² - 17W + 6
                  (3W - 2)(4W - 3)
Change the parentheses to brackets, then replace the
W's with (x + 1)
              [3(x + 1) - 2][4(x + 1) - 3]
                [3x + 3 - 2]{4x + 4 - 3]
                    (3x + 1)(4x + 1)   
Edwin
AnlytcPhil@aol.com