1.因为an,sn,an²成等差数列,知道2Sn=an+an²an=Sn-Sn-1=an(1+an) /2 - an-1(1+an-1) /2得2an=an+an²-an-1-an-1²an²-an-an-1-an-1²=0(an-an-1)(an+an-1)=an+an-1①因...