Réponse:
bonjour
Explications étape par étape:
on simplifie donc
1/2×2/3×3/4×4/5
= 1/3×3/4×4/5 (car 1/2×2/3 on simplifie le 2 donc 1/3)
= 1/4×4/5
=1/5
25/16×12/15
=25/16×4/5(car on simplifie 12 et 15 par 3 )
=5/16×4 (car on simplifie le 25 et le 5)
=5/4
15/39×26/25×28/42
= 5/13×26/25×2/3
=5×2/35×2/3
=2/7×2/3
=4/21