Salut,
a = 1/5+3/7+1/7+4/5+3/7 (aduc la același numitor : 35)
a = 7/35+15/35+5/35+28/35+15/35
a = 22/35+33/35+15/35
a = 55/35+15/35
a = 70/35
a = 2.
b = 3/10-2/9+7/10-7/9 (aduc la același numitor : 90)
b = 27/90-20/9+63/90-70/90
b = 7/90-7/90
b = 0.
a×b = 2×0 = 0.
Succes! :3
