Sagot :
Bonjour
A = 14/5 - 6/5 x 7/18
A = 14/5 - 42/90
A = (14 x 3) / (5 x 3) - (6 x 7) / (6 x 15)
A = 42/15 - 7/15
A = 35/15
A = (5 x 7) / (5 x 3)
A = 7/3
B = (1/5 - 5/4) : 7/5
B = [(1 x 4) / (5 x 4) - (5 x 5) / (4 x 5)] : 7/5
B = (4/20 - 25/20) : 7/5
B = (- 21/20) x 5/7
B = - 105/140
B = (35 x - 3) / (35 x 4)
B = - 3/4.
Bjr,
14/5 - 6/5 * 7/18 = 14/5 - 42/90 = 252/90 - 42/90 = 210/90 = (30 * 7)/(30 * 3) = 7/3
(1/5 - 5/4) * 5/7 = (4/20 - 25/20) * 5/7 = - 21/20 * 5/7 = -105/140 = (-7 * 15)/(20 * 7) = -15/20 = -3/4.