soluzione
Scomporre
x
2m
- 2x
m
y - x
2n
+ y
2
=
= (x
2m
- 2x
m
y + y
2
) - x
2n
=
= (x
m
- y)
2
- x
2n
=
= [(x
m
- y) - x
n
] [(x
m
- y) + x
n
] =
= (x
m
- y - x
n
) (x
m
- y + x
n
) =
= (x
m
- x
n
- y) (x
m
+ x
n
- y)