1.
3/1*2=1+1/2
5/2*3=1/2+1/3
……
2005/1002*1003=1/1002+1/1003
因此,原式=-1+1/1003=-1002/1003
2.
原式=(1-2+3-4-5+6-7+8-9)+(1/2-5/6+1/12-19/20-1/30+41/42-1/56+71/72-1/90)
=-9+(1/2+1/6+1/12+1/20-1/30-1/42-1/56-1/72-1/90)
=-9+(1-1/2+1/2-1/3+1/3-1/4+1/4-1/5-(1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10))
=-9+(1-1/5-1/5+1/10)
=-8.3