2004*2005-1分之2004+2005*2003
=(2004+(2004+1)(2004-1))/(2004*2005-1)
=(2004+2004*2004-1)/(2004*2005-1)
=(2004*2005-1)/(2004*2005-1)
=1
2004*2005-1分之2004+2005*2003
=(2004+(2004+1)(2004-1))/(2004*2005-1)
=(2004+2004*2004-1)/(2004*2005-1)
=(2004*2005-1)/(2004*2005-1)
=1