Répondre :
a=-8/28
b=1/35
c=-45/21
a-b+c=
-8/28-1/35+(-45/21)=
-8/28-1/35-45/21=
-2/7-1/35-15/7=
-10/35-1/35-75/35=-86/35
b-a-c=
1/35-(-8/28)-(-45/21)=
1/35+8/28+45/21=
1/35+2/7+15/7=
1/35+10/35+75/35=86/36
b=1/35
c=-45/21
a-b+c=
-8/28-1/35+(-45/21)=
-8/28-1/35-45/21=
-2/7-1/35-15/7=
-10/35-1/35-75/35=-86/35
b-a-c=
1/35-(-8/28)-(-45/21)=
1/35+8/28+45/21=
1/35+2/7+15/7=
1/35+10/35+75/35=86/36