soluzione
Scomporre
x
6
y
6
- z
6
+ x
3
y
3
+ z
3
=
= (x
3
y
3
- z
3
) (x
3
y
3
+ z
3
) +(x
3
y
3
+ z
3
) =
= (x
3
y
3
+ z
3
) [(x
3
y
3
- z
3
) + 1] =
=(xy + z) (x
2
y
2
- xyz + z
2
) (x
3
y
3
- z
3
+ 1)