(1-1/2-1/3-...-1/2001)*(1/2+1/3+...1/2002)-(1-1/2-1/3-...1/2002)*(1/2+1/3+...+1/2001)

来源:百度知道 编辑:UC知道 时间:2024/05/12 16:32:43
1-1/2-1/3-...-1/2001)*(1/2+1/3+...1/2002)-(1-1/2-1/3-...1/2002)*(1/2+1/3+...+1/2001)

设(1/2+1/3+...1/2001)为X,(1/2+1/3+...1/2002)为Y,原式则可以写为:
(1-X)*Y-(1-Y)*X
=Y-XY-X+XY
=Y-X
=1/2002

(1-1/2-1/3-...-1/2001)*(1/2+1/3+...1/2002)-(1-1/2-1/3-...1/2002)*(1/2+1/3+...+1/2001)
=(1-1/2-1/3..-1/2001)(1/2+1/3+...1/2001)+(1-1/2-1/3..1/2001)*1/2002-[(1-1/2-1/3...-1/2001)(1/2+1/3+...1/2001)-1/2002*(1/2+1/3+...1/2001)
=(1-1/2-1/3..-1/2001)(1/2+1/3+...1/2001)+(1-1/2-1/3..1/2001)*1/2002-(1-1/2-1/3...-1/2001)(1/2+1/3+...1/2001)+1/2002*(1/2+1/3+...1/2001)
=1/2002*(1-1/2-1/3-1/2001+1/2+1/3+...1/2001)
=1/2002*1
=1/2002

(1-1/2-1/3-...-1/2001)*(1/2+1/3+...1/2002)-(1-1/2-1/3-...1/2002)*(1/2+1/3+...+1/2001)
=(1-1/2-1/3..-1/2001)(1/2+1/3+...1/2001)+(1-1/2-1/3..1/2001)*1/2002-[(1-1/2-1/3...-1/2001)(1/2+1/3+...1/2001)-1/2002*(1/2+1/3+...1/2001)
=(1-1/2-1/3..-1/2001)(1/2+1/3+...1/2001)+(1-1/2-1/3..1/2001)*1/2002-(1-1/2-1/3...-1/2001)(1/2+1/3+...1/2001)+1/2002*(1/2+1/3+...1/2001)
=1/2002*(1-1/2-1/3-1/2001+1/2+1/3+...1/2001)