exercice 2 du DM6
A= 2/3- 5/7-1/3+2/7+8/3-3/7
=2/3-1/3+8/3-5/7+2/7-3/7
=9/3-9/7
=63/21-18/21
=45/21
B= 3/4-1/6+1/4-2/3+7/6-1/3
=3/4+1/4-1/6+7/6-2/3-1/3
=4/4-6/6-3/3
=1-1-1
=1-2
=-1
C=2-3/5-1/2-2/5-3/2
=2-3/5-2/5-1/2-3/2
=2-5/5-3/2
=2-1-3/2
=1-3/2
=2/2-3/2
=1/2
D=5/16+7/15-3/16+2/15-1/8+2/5
=5/16-3/16+7/15+2/15-1/8+2/5
=2/16+9/15-2/16+6/15
=9/15+6/15
=15/15
=1
