Bonjour,
25)
a) 1/2 + 7/5 = (1 x 5) / (2 x 5) + (7 x 2) / (5 x 2) = 5/10 + 14/10 = 19/10
b) 8/7 - 7/12 = (8 x 12) / (7 x 12) - (7 x 7) / (12 x 7) = 96/84 - 49/84 = 47/84
c) 2/23 - 11/10 = (2 x 10) / (23 x 10) - (11 x 23) / (10 x 23) = 20/230 - 253/230 = - 230/230 = 1
d) - 3/4 - 7/9 = (- 3 x 9) / (4 x 9) - (7 x 4) / (9 x 4) = - 27/36 - 24/36 = - 51/36 = (3 x - 17) / (3 x 12) = - 17/12
Pour le 28 tu procèdes de la même façon
