An=Sn-S(n-1)=[(Sn)^0.5+(S(n-1))^0.5]×[(Sn)^0.5-(S(n-1))^0.5] 2An=[(Sn)^0.5+(S(n-1))^0.5] 两式相除 [(Sn)^0.5-(S(n-1))^0.5]=0.5 2an=√Sn + √Sn-1)=2√Sn -0.5 2an+0.5=√Sn 2a(n+1)+0.5=√S(n+1) 2[a(n+1)-...