作业帮1/1*2+1/2*3+1/3*4...1/19*20=?
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1/1*2+1/2*3+1/3*4...1/19*20=?
1/1*2+1/2*3+1/3*4...1/19*20=?
1/1*2+1/2*3+1/3*4...1/19*20=?
1/1*2+1/2*3+1/3*4...1/19*20=1-1/20=19/20
1/1*2+1/2*3+1/3*4...1/19*20
原式=1-1/2+1/2-1/3+........+1/19-1/20
中间的抵消
=1-1/20
=19/20
1+2+3+4.
1+2+3+4.
1+2+3+4.+1000
1+2+3+4.+101
1+2+3+4..100000000
1+2+3+4.=
1+1+2+3+4.+99
1+2+3+4.=1/12?
1/1+2+1/1+2+3+1/1+2+3+4+...+1/1+2+3+4...+992+1分之1加1+2+3/1这样
1/1*2+1/2*3+1/3*4.+1/2011*2012+1/2012*2013
1/1*2+1/2*3+1/3*4...+1/99*100+1/(2011*2012)
（1-1/2-1/3-1/4..-1/2004)*(1+1/2+1/3+1/4+...+1/2005)-(1-1/2-1/3-1/4-...-1/2005)*(1+1/2+1/3+1/4+...+1/2004)
(1)计算1/1*2+1/2*3+1/3+4.+1/99*100 (2)1/1*3+1/3*5+1/5*7.+1/49*51
1/1*2+1/2*3+1/3*4...1/19*20=?
1/1乘2+1/2乘3+1/3乘4.+1/199乘200
1/1*2+1/2*3+1/3*4.+1/2003*2004
1/1×2+1/2×3+1/3×4...+1/2006×2007=?
1/1*2+1/2*3+1/3*4.+1/99*100这道题怎么做