reserve a,b,c for positive Real,
  m,x,y,z for Real,
  n for Nat,
  s,s1,s2,s3,s4,s5 for Real_Sequence;

theorem Th13:
  (a|^3+b|^3+c|^3)/3>=a*b*c
proof
  (a|^3+b|^3+c|^3)/3>=(3*a*b*c)/3 by Th12,XREAL_1:72;
  hence thesis;
end;
