Quel expression ne se factorise pas en 2(n+1) ? Merci

bonjour

3 n ( n + 1) - ( 3 n - 2) ( n + 1)

=  ( n + 1 ) ( 3 n - 3 n + 2 )

= ( n + 1 ) ( 2)

3 ( n + 3) - n - 7

=  3 n + 6 - n - 7

=  2  n  -  1

2 ( n - 1 ) + 4

= 2 n - 2 + 4

=  2 n + 2

=  2 ( n + 1 )

3 ( n + 1 ) - n + 1

= 3 n + 3 -  n + 1

=  2 n + 4

= 2 ( n + 2 )

4 n + 4 - 2 n - 2

=  2 n + 2

= 2 ( n + 1 )

(10 n + 10 ) / 5

= 2 n + 2

= 2 ( n + 1 )

( 5 n + 1) / 2 - ( n + 1 ) / 2

=  ( 5 n + 1 - n - 1 ) / 2

=    4 n /2

= 2 n

6 ( n - 1 ) - 4 ( n - 2 )

= 6 n - 6 - 4 n + 8

= 2 n + 2

=  2 ( n + 1 )