Bonjour;

1)

2ab +ac +3ac -2c

= 2ab +4ac -2c

2)

y-4 +5y +30

= 6y +26

1) a ( 2b + c ) + c ( 3a - a ) =

= ( a × 2b + a × c ) + ( c × 3a - 2 )    

= ( a × 2b + ac ) + ( c × 3a - 2c)

2) 3 ( y - 4 ) + 5 ( y + 6 ) =

= ( 3 × y - 3 × 4 ) + ( 5 × y + 5 × 6)

= ( 3y - 12 ) + ( 5y + 30)