Question

已知a、b互为相反数，c、d互为倒数

求3a+3b-21/6cd+3的值
还有题 若a +b=0,则a/b的值为 A-1 b0 c无意义 D-1或无意义

Answer 1

已知a、b互为相反数，c、d互为倒数
a+b=0
cd=1
3a+3b-21/6cd+3
=3(a+b)-21/6cd+3
=3*0-21/6*1+3
=-0.5
若a +b=0,则a/b的值为-1

Answer 2

∵a、b互为相反数，c、d互为倒数
∴a+b=0 c*d=1
∴3a+3b-21/6cd+3
=3(a+b)-21/6cd+3
=0-7/2+3
=-1/2

Answer 3

3a+3b-21/6cd+3
=0-21/6+3
=-1/2

-1

Answer 4

3a+3b-21/6cd+3
=0-21/6+3
=-1/2

若a +b=0,则a/b的值为0或-1 （ab互为相反数，包括0）

追问

若a +b=0,则a/b的值为 A-1 b0 c无意义 D-1或无意义