1/1*2+1/2*3+1/3*4+L;+1/n(n+1)= 1/2*4+1/4*6+1/6*8+L+1/2006*2008=
问题描述:
1/1*2+1/2*3+1/3*4+L;+1/n(n+1)= 1/2*4+1/4*6+1/6*8+L+1/2006*2008=
答
1/1*2+1/2*3+1/3*4+L;+1/n(n+1)= 1-1/2+1/2-1/3+1/3.+1/n-1/(n+1)=1-1/(n+1)1/2*4+1/4*6+1/6*8+L+1/2006*2008=1/2(1/1*2+1/2*3+1/3*4.+1/1003-1/1004)=1/2(1-1/2+1/2-1/3+1/3...-1/1004)=1/2(1-1/2004)=1/2*2003/2...