Respostas

2014-05-07T17:00:55-03:00
10xy - [ - 3xy + ( 9xy - 2xy ) - xy ]
10xy - [ - 3xy + 7 xy - xy ]
10xy - [ 3 xy ]
10xy - 3xy
7xy
2 4 2
2014-05-07T17:01:07-03:00
10xy - [ -3xy + (9xy - 2xy) - xy]
10xy - [ -3xy + 7xy - xy]
10xy - 5xy
5xy é a resposta