Respostas

2014-01-15T21:15:22-02:00

(7a+1)(7a-1)= (7a)^2-1^2=49a-1
1 1 1
2014-01-15T21:20:56-02:00
(7a + 1) . (7a - 1) =
49a² - 7a + 7a - 1 =
49a² - 1
3 4 3