(1-1/2)+(1/2-1/3)+(1/3-1/4)+···+(1/2009-1/2010)
根据等式关系,把括号去掉,原式变为
1-1/2+1/2-1/3+1/3-1/4+···+1/2009-1/2010
=1+(-1/2+1/2)+(-1/3+1/3)+···--1/2010
括号内相加得0
则=1-1/2010=2009/2010
即(1-1/2)+(1/2-1/3)+(1/3-1/4)+···+(1/2009-1/2010)=2009/2010
第一个括号的-1/2和第二个括号的+1/2正好抵消
后面依此类推
则=1-1/2010=2009/2010