
1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+...+1/9*100=?
展开全部
裂项法:
1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+...+1/99*100
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+……+1/99-1/100
=1-1/100
=99/100
1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+...+1/99*100
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+……+1/99-1/100
=1-1/100
=99/100
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