soluzione
Scomporre
27a
3
x
3
- 27a
2
x
2
+ 9ax -1 - x
3
=
= (3ax - 1)
3
- x
3
=
= [(3ax-1) - x] [(3ax - 1)
2
+ x(3ax-1) + x
2
] =
= (3ax - 1 - x) (9a
2
x
2
- 6ax + 1 + 3ax
2
- x + x
2
)