a,b互为相反数,a=-b a+b=0
b,c互为倒数,bc=1
m³=m
m(m²-1)=0
m(m+1)(m-1)=0
m=0或m=-1或m=1
(2a+2b)÷(m+2)
=2(a+b)/(m+2)
=0