2005*2003/2004+1/2004
=[(2004+1)(2004-1)+1]/2004
=(2004²-1+1)/2004
=2004²/2004
=2004
5/3*1/13+5/9*3/13+5/18*6/13
=5/3×1/13+5/3×1/13+5/3×1/13
=5/3×1/13×3
=5/13
这样就简便了,刚才真麻烦
2005*2003/2004+1/2004
=[(2004+1)(2004-1)+1]/2004
=(2004²-1+1)/2004
=2004²/2004
=2004
5/3*1/13+5/9*3/13+5/18*6/13
=5/3×1/13+5/3×1/13+5/3×1/13
=5/3×1/13×3
=5/13
这样就简便了,刚才真麻烦