soluzione
Scomporre
2x
4
- 2y
4
+ 8x
2
- 8y
2
=
= 2(x
4
- y
4
+ 4x
2
- 4y
2
) =
= 2[(x
2
- y
2
) (x
2
+ y
2
) + 4(x
2
- y
2
)] =
= 2(x
2
- y
2
) [(x
2
+ y
2
) + 4] =
= 2(x - y) (x + y) (x + y)
2
=
= 2 (x - y) (x + y)
3