因为an=sn-s(n-1)=3a(n+1)-3an
所以a(n+1)=4/3 an
{1,4/3,16/9,......}
an=(4/3)的n-1次幂
n=1 ,a1=1/4(a1+1)²,得到a1=1
s(n-1)=sn-an
1/4[a(n-1)+1]²=1/4(an+1)²-an
[a(n-1)+1]²=(an+1)²-4an=(an-1)²
a(n-1)+1=an-1
an=a(n-1)+2
{1,3,5,.....}
an=2n-1
an=根号下(an)²+1 题目错误