reserve x for set;
reserve a, b, c, d, e for Real;
reserve m, n, m1, m2 for Nat;
reserve k, l for Integer;
reserve p for Rational;

theorem Th18:
  a>=1 & n>=1 implies n-root a >= 1 & a >= n-root a
proof
  assume that
A1: a>=1 and
A2: n>=1;
   n -Root a >= 1 & a >= n -Root a by A1,A2,PREPOWER:29;
  hence thesis by A2,Def1;
end;
