xlist = linspace ( 0, 4, 201 );
ylist = f123 ( xlist );
plot ( xlist, ylist, xlist, 0*ylist, 'k:', 'LineWidth', 3 )
grid on
xlabel ( '<-- X -->' )
ylabel ( '<-- Y -->' )
title ( 'y=(x-1)*(x-2)*(x-3)', 'Fontsize', 24 )
print ( '-djpeg', 'f123.jpg' )