[newbie question] solving fifth order polynomial equation



When solving the following equation
solve(1+11*s+45*s^2+84*s^3+70*s^4+21*s^5=0);

Maxima shows two real solutions and three complex ones in stead of five 
real solutions.
Besides the solutions s=-1 and s=-1/3, I think there are also a real 
solutions around  s=-2.63024e-01, s=-4.08991e-01 and s=-1.32799

Can anyone explain what is going wrong and how to solve it?

reagards,
hugo