I thought that expand returned a simplified expression; maybe it does not:
(%i241) (1-sqrt(5))^3-4*(1-sqrt(5))^2+8;
(%o241) (1-sqrt(5))^3-4*(1-sqrt(5))^2+8
(%i242) expand(%);
(%o242) 5^(3/2)-5^(3/2)
(%i243) expand(%,0,0);
(%o243) 0
Ratexpand crunches this to zero without the additional simplification:
(%i244) ratexpand((1-sqrt(5))^3-4*(1-sqrt(5))^2+8);
(%o244) 0
--Barton