计算(1-1/2-1/3-...-1/2010)*(1/2+1/3+..+1/2011)-(1-1/2-1/3-...-1/2011)*(1/2+1/3+...+1/2010)
问题描述:
计算(1-1/2-1/3-...-1/2010)*(1/2+1/3+..+1/2011)-(1-1/2-1/3-...-1/2011)*(1/2+1/3+...+1/2010)
答
=(1-1/2-1/3-...-1/2010)*(1/2+1/3+..+1/2010)+1/2011(1-1/2-1/3-...-1/2010)-(1-1/2-1/3-...-1/2010)*(1/2+1/3+...+1/2010)+1/2011(1/2+1/3+...+1/2010)
=1/2011(1-1/2-1/3-...-1/2010)-1/2011(1/2+1/3+...+1/2010)
=1/2011[ (1-1/2-1/3-...-1/2010)-(1/2+1/3+...+1/2010) ]
而后自己计算
答
令k=1/2+1/3+...+1/2010,则原式=(1-k)(k+1/2011)-(1-k-1/2011)k
=(k+1/2011-k^2-k/2011)-(k-k^2-k/2011)
=1/2011