(1/2+1/3+...+1/2005)(1+1/2+1/3+...+1/2004)-(1+1/2+...+1/2005)(1/2+1/3+...+1/2004)不用设未知数怎么解?

来源：学生作业学帮网编辑：学帮网时间：2024/05/31 22:29:51

=[(1/2+1/3+...+1/2004)+1/2005][1+(1/2+1/3+...+1/2004)]-[1+(1/2+1/3+...+1/2004)+1/2005](1/2+1/3+...+1/2004)
=(1/2+1/3+...+1/2004)×1+(1/2+1/3+...+1/2004)^2+1/2005+](1/2+1/3+...+1/2004)×1/2005-1×(1/2+1/3+...+1/2004)-(1/2+1/3+...+1/2004)^2=1/2005×(1/2+1/3+...+1/2004)
=1/2005