Réponses

2014-05-09T13:22:28+02:00
B= -2/5*(2/7-1/3)
= -2/5*(2*3/7*3 -1*7/3*7)
= -2/5*(6/21 -7/21)
= -2/5*-1/21
= 2/105

D= 1/2+2/3+3/4+4/5+5/6
=3/6 +4/6+15/20+16/20+5/6
=12/6+31/20
= 240/120 +186/120
= 426/120
= 71*6/20*6
= 71/20