(1/2+1/3+...+1/2009)(1+1/2+1/3+...+1/2008)-(1+1/2+...+1/2009)(1/2+1/3+...1/2008)
来源:学生作业帮助网 编辑:作业帮 时间:2024/11/23 21:59:02
(1/2+1/3+...+1/2009)(1+1/2+1/3+...+1/2008)-(1+1/2+...+1/2009)(1/2+1/3+...1/2008)
(1/2+1/3+...+1/2009)(1+1/2+1/3+...+1/2008)-(1+1/2+...+1/2009)(1/2+1/3+...1/2008)
(1/2+1/3+...+1/2009)(1+1/2+1/3+...+1/2008)-(1+1/2+...+1/2009)(1/2+1/3+...1/2008)
令a=1/2+1/3+...+1/2008
原式=(a+1/2009)(1+a)-(1+a+1/2009)a
=a(1+a)+1/2009(1+a)-a(1+a)-1/2009a
=1/2009(1+a)-1/2009a
=1/2009+1/2009a-1/2009a
=1/2009
0
令a=1/2+1/3+...+1/2008
原式=(a+1/2009)(1+a)-(1+a+1/2009)a
=a(1+a)+1/2009(1+a)-a(1+a)-1/2009a
=1/2009(1+a)-1/2009a
=1/2009+1/2009a-1/2009a
=1/2009
(1/2+1/3+...+1/2009)(1+1/2+1/3+...+1/2008)-(1+1/2+...+1/2009)(1/2+1/3+...1/2008)=
(1/2+1/3+...+1/2009)+(1/2+1/3+...+1/2009)(1/2+1/3+...+1/2008)-(1/2+1/3+...1/2008)-
(1/2+...+1/2009)(1/2+1/3+...1/2008)=1/2009