a,b互为相反数,
a+b=0
c,d互为倒数,
cd=1
m的绝对值为3,
m=±3
当m=3时
(a+b)/5+3m-cd
=0/5+3*3-1
=9-1
=8
当m=-3时
(a+b)/5+3m-cd
=0/5+3*(-3)-1
=-9-1
=-10