1+ 1/(1+2)+1/(1+2+3)+1/(1+2+3+4)+……+1/(1+2+3+……+100)
问题描述:
1+ 1/(1+2)+1/(1+2+3)+1/(1+2+3+4)+……+1/(1+2+3+……+100)
答
1+1/(1+2)+1/(1+2+3)+1/(1+2+3+4)...+1/(1+2+3+...100)=1+2/2*3+2/3*4+2/4*5+...+2/100*101=1+2*(1/2*3+1/3*4+1/4*5+...+1/100*101)=1+2*(1/2-1/3+1/3-1/4+1/4-1/5+...+1/99-1/100+1/100-1/101)=1+2*(1/2-1/...