(1+3+5+7+....+2005)-(2+4+6+...2006)=?? -1/2-1/6-1/12-1/20-1/30-1/42-......-1/90-1/110=??急！！
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(1+3+5+7+....+2005)-(2+4+6+...2006)
=(1-2)+(3-4) +(5-6)+------+(2005-2006)
=-1-1-1-------1
=-1003
-1/2-1/6-1/12-1/20-1/30-1/42-......-1/90-1/110
=-(1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+-----+1/9-1/10+1/10-1/11)
=-(1-1/11)
=-10/11
=(1-2)+(3-4) +(5-6)+------+(2005-2006)
=-1-1-1-------1
=-1003
-1/2-1/6-1/12-1/20-1/30-1/42-......-1/90-1/110
=-(1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+-----+1/9-1/10+1/10-1/11)
=-(1-1/11)
=-10/11
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