| 1  1  X |
   | 1  X  1 | 
   | X  1  1 |
   | 1  1  X |=  |  1   1     X  | = |X-1   1-X |
   | 1  X  1 |    |  0  X-1  1-X |   |1-X  1-X^2|
   | X  1  1 |    | 0  1-X  1-X^2|
   =(1-x)^2 | -1   1  | = -(x+2)(1-x)^2
            | 1   1+x |