/ ___\ / ___\ / ___\ / ___\
| 1 I*\/ 3 | | 1 I*\/ 3 | | 1 I*\/ 3 | | 1 I*\/ 3 |
(a + 1)*(a - 1)*|a + - + -------|*|a + - - -------|*|a + - - + -------|*|a + - - - -------|
\ 2 2 / \ 2 2 / \ 2 2 / \ 2 2 /