(a+b+c)(a+b- c)=[( )+( )][( )- ( )]

问题描述:

(a+b+c)(a+b- c)=[( )+( )][( )- ( )]
(a- b+c)(a+b- c)=[( )+( )][( )- ( )]
(a+b+c)(a- b- c)=[( )+( )][( )- ( )]

1.[ (a+b)+(C)][(a+b)-(c)]
2. [a+(b-c)][a-(b-c)]
3. [a+(b+c)][a-(b+c)]