有道数学题您看看有没有规律可寻或怎样解答:1-1/2+1/3-1/4+1/5-1/6+1/7·····+1/2009-1/20
具体是这样的:1-1/2+1/3-1/4+1/5-1/6+1/7·····+1/2009-1/2010=