若a,b满足{a+2b=8,2a+b=7则a-b=

来源:学生作业帮助网 编辑:六六作业网 时间:2024/05/24 23:49:20
若a,b满足{a+2b=8,2a+b=7则a-b=若a,b满足{a+2b=8,2a+b=7则a-b=若a,b满足{a+2b=8,2a+b=7则a-b=a-b=(2a+b-a-2b)=(2a+b)-(a

若a,b满足{a+2b=8,2a+b=7则a-b=
若a,b满足{a+2b=8,2a+b=7则a-b=

若a,b满足{a+2b=8,2a+b=7则a-b=
a-b
=(2a+b-a-2b)
=(2a+b)-(a+2b)
=7-8
=-1

2a+b=7 减去 a+2b=8
∴a-b=-1

2a+b-(a+2b)=-1
2a+b-a-2b=-1
2(a-b)+b-a=-1
2(a-b)-(a-b)=-1
a-b=-1

负一