ab互为倒数
ab=1
cd互为相反数
c+d=0
d=-c
|e|=3
e=±3
当e=3时
2ab+(c-d)+3/e
=2+(c-(-c))+3/3
=2+2c+1
=3+2c
当e=-3时
2ab+(c-d)+3/e
=2+(c-(-c))+3/-3
=2-1+2c
=1+2c