Bonsoir! J evais essayer a t'aider! :)
Ex17
A = 5 * 2/3
A = 5/1 * 2/3
A = 10/3
B = -7/5 * 4
B = -7/5 * 4/1
B = -28/5
C = 5/6 * -11/4
C = -55/24
D = -8/9 * -10/9
D = 80/81
Ex18
A = 8/7 * .... = 16/63
.... = 16/63 : 8/7
.... = 16/63 * 7/8
.... = 112/504
B = -5 * 4/y = x/9
y = -9
-5 = -5/-1
x = -20
Donc, B = -5/-1 * 4/-9 = -20/9
Ex19
A = -5/9 * -2/17 = + ...
B = 3/-9 * -2/-5 = -....
C= - -4/5 * -3/25 = -....
D = -1/-7 * -2/-5 = +...
Voila, j'espere avoir aide! :)
