2004×2004/(2004×2005×2005)-2004
=2004/(2005×2005)-2004
=2004/(2005×2005)-2004×2005×2005/(2005×2005)
=2004×(1-2005×2005)/(2005×2005)
=2004×(-4020024)/(2005×2005)
=-8056130100/4020025
=-322245204/160801
2004×2004/(2004×2005×2005)-2004
=2004/(2005×2005)-2004
=2004/(2005×2005)-2004×2005×2005/(2005×2005)
=2004×(1-2005×2005)/(2005×2005)
=2004×(-4020024)/(2005×2005)
=-8056130100/4020025
=-322245204/160801