数列{an}满足a1＝1,a2＝2,an＋2＝2an＋1－an＋2
问题描述：
数列{an}满足a1＝1,a2＝2,an＋2＝2an＋1－an＋2
答
（Ⅰ）由an+2=2an+1-an+2得,an+2-an+1=an+1-an+2,由bn=an+1-an得,bn+1=bn+2,即bn+1-bn=2,又b1=a2-a1=1,所以{bn}是首项为1,公差为2的等差数列．（Ⅱ）由（Ⅰ）得,bn=1+2（n-1）=2n-1,由bn=an+1-an得,an+1-an=2n-1,则a...你再写一项bn+1=an+2-an+1 bn=an+1-an
带入到an+2-an+1=an+1-an+2式中就是bn+1=bn+2，bn+1-bn=2