n次方差公式的证明方法 n次方差公式: anbn(ab)(an1an2ban3b2abn2bn1),nN 证法一: anbnanan1ban1ban2b2an2b2.....abn1bn an1(ab)an2b(ab).....bn1(ab)(ab)(a 证法二: n1an2b.....bn1) b设等比数列an的通项公式为an,则其前n项和为: a nbnbb1b123n1nabbbaab(anbn)bb......nbaaaaba(ab)aa1a23n1n na(ab)bbbbb故:anbn......baaaaan (ab)an1an2ban3b2......abn2bn1 本文来源:https://www.wddqw.com/doc/b6caa34bdeccda38376baf1ffc4ffe473268fd44.html