bonsoir;

1)

3/7 = 0,42857...

4,2 /5 = 0,84

1,8/3 = 0,6

faux

2)

-12x² +10x -18x +15 = -12x² -8x +15

et

-12x² +3x -11x +15 = - 12x² -8x +15

vrai

3)

12/2 = 6

6/2 =3

=> 2*2*3

18/2 = 9

9/3 =3

=> 2*3*3

6/2 = 3

=>2*3

Vrai