Tính A=$\frac{1}{2!}+\frac{2}{3!}+\frac{3}{4!}+...+\frac{99}{100!}$
Dãy số có quy luật
Started By habayern, 23-02-2014 - 21:35
#1
Posted 23-02-2014 - 21:35
#2
Posted 23-02-2014 - 21:50
Ta có
$A=\frac{2-1}{2!}+\frac{3-1}{3!}+\frac{4-1}{4!}+...+\frac{100-1}{100!}=1-\frac{1}{2!}+\frac{1}{2!}-\frac{1}{3!}+\frac{1}{3!}-\frac{1}{4!}+...+\frac{1}{99!}-\frac{1}{100!}=1-\frac{1}{100!}$
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