萍乡莲花县委书记是谁:1/10+1/40+...+1/340=? 3/20+3/30+...+3/9900=?
来源:百度文库 编辑:高校问答 时间:2024/10/06 00:33:56
写出过程
解:1/10+1/40+...+1/340
=1/2*5+1/5*8+1/8*11+...+1/17*20
=(1/3)(1/2-1/5+1/5-1/8+1/8-1/11+...+1/17-1/20)
=(1/3)(1/2-1/20)
=3/20
2.3/20+3/30+...+3/9900
=3(1/20+1/30+...+1/9900)
=3(1/4*5+1/5*6+1/6*7+...+1/99*100)
=3(1/4-1/5+1/5-1/6+...+1/99-1/100)
=3(1/4-1/100)
=3(96/400)
=288/400
=18/25
1/10+1/40+...+1/340=? 3/20+3/30+...+3/9900=?
齐齐算 1/(10/1+12/1)
1/6+1/8+1/10+1/12+..........+1/202=?
一:1/8=1/( )+1/( )二:1/10=1/( )+1/( )三:1/12=1/( )+1/( )+1/( )
1+1/1+2+1/1+2+3+......+1/1+2+3+......+10
1/6+1/24+1/60+1/40=
-1/10-1/11-1/11-1/12-…-1/19-1/20
(1-1/2^2)(1-1/3^2)....(1-1/10^2)
(1-1/2^2)(1-1/3^2)....(1-1/10^2)
1/4+1/12+1/24+1/40+……+1/19800=?