Respostas

2014-05-25T23:01:51-03:00
F(x)= -7x + 21
-7x+21=0
-7x= -21 .(-1)
 7x= 21
  x= 21
       7
 x= 3
2014-05-26T00:24:56-03:00
-7x + 21 = 0
-7x = -21
x = -21
       -7
x = 3