A-B=(-1/3+2.5)-(-11.5+4.5)
=-1/3+2.5+11.5-4.5
=9.5-1/3>0
所以A大于B
M-N=[-1/7-(-2/7)]-[1.4-(-1.2)-2.5]
=(-1/7+2/7)-(1.4+1.2-2.5)
=1/7-0.1
=10/70-7/70
=3/70>0
所以M大于N
A-B=(-1/3+2.5)-(-11.5+4.5)
=-1/3+2.5+11.5-4.5
=9.5-1/3>0
所以A大于B
M-N=[-1/7-(-2/7)]-[1.4-(-1.2)-2.5]
=(-1/7+2/7)-(1.4+1.2-2.5)
=1/7-0.1
=10/70-7/70
=3/70>0
所以M大于N