Réponse ex 1 :
1.
60 = 2 × 2 × 3 × 5
40 = 2 × 2 × 2 × 5
126 = 2 × 3 × 3 × 7
198 = 2 × 3 × 3 × 11
105 = 3 × 5 × 7
90 = 2 × 3 × 3 × 5
2.
60/40 = 3/2
126/198 = 7 /11
105/90 = 7/3x2 = 7/6
