Question

（6分）觀察下面的變形規(guī)律：
 ＝1－； ＝－；＝－；……
解答下面的問題：
（1）若n為正整數(shù)，請你猜想＝                  ；
（2）證明你猜想的結論；
（3）求和：＋＋＋…＋ .

Answer 1

（1）·············································································· 1分
（2）證明：－＝－＝＝.····················· 3分
（3）原式＝1－＋－＋－＋…＋－
＝.································································· 5分

略