Respostas

2014-08-07T13:38:23-03:00
(2+5i).(2-5i)-(9+i)
4-10i+10i-25i²-(9+i)=0
4-25(-1)-9+i=0
2+25-9+i=0
18+i=0

2014-08-07T13:59:08-03:00
(2 + 5i) * (2 - 5i) = 4 - 25i^2

Só que i^2 = -1, logo:

(2 + 5i) * (2 - 5i) = 4 + 25 = 29

29 - (9 + i) = 20 - i

Conjugado de 20 - i = 20 + i

Resposta: 20 + i