1998x(1/11-1/2009)+11x(1/1998-1/2009)-2009x(1/11-1/1998)+3 =

1998x(1/11-1/2009)+11x(1/1998-1/2009)-2009x(1/11-1/1998)+3 =
1998x(1/11-1/2009)+11x(1/1998-1/2009)-2009x(1/11-1/1998)+3 =

1998x(1/11-1/2009)+11x(1/1998-1/2009)-2009x(1/11-1/1998)+3 =
原式=1998/11-1998/2009+11/1998-11/2009-2009/11+2009/1998+3
=(1998/11-2009/11)-(1998/2009+11/2009)+(11/1998+2009/1998)+3
=-1-1+2020/1998+3
=4018/1998
=2009/999

=1998/11-1998/2009+11/1998-11/2009-2009/11+2009/1998+3
=-11/11-2009/2009+2020/1998+3
=-1-1+1+22/1998+3
=2+11/999