function quartic_gauss_m1p1 ( n )

%*****************************************************************************80
%
%% quartic_gauss_m1p1 estimates integral (-1<=x<=1) quartic(x) dx.
%
%  Input:
%
%    integer n: the number of points in the Gauss rule.
%
  a = -1.0;
  b = +1.0;
  q_exact = quartic_int ( -1.0, +1.0 );

  [ xi, rho ] = gauss ( n );
  q_gauss = rho' * quartic(xi);

  e = q_exact - q_gauss;

  fprintf ( 1, '\n' );
  fprintf ( 1, 'quartic_gauss_m1p1:\n' );
  fprintf ( 1, '  Gauss quadrature of quartic(x)\n' );
  fprintf ( 1, '  Interval = [%g,%g]\n', a, b );
  fprintf ( 1, '  N = %d\n', n );
  fprintf ( 1, '  I(quartic(),a,b)  = %g\n', q_exact );
  fprintf ( 1, '  Gn(quartic(),a,b) = %g\n', q_gauss );
  fprintf ( 1, '  E = I-G          = %g\n', e );

  return
end

