an=Sn-Sn-1=1/2(根号Sn+根号Sn-1)
(根号Sn-根号Sn-1)(根号Sn+根号Sn-1)=Sn-Sn-1
根号Sn-根号Sn-1=1/2
根号Sn为等差数列 且根号S2=2 公差d=1/2
根号S10=根号S2+0.5*6=5
S10=25
an=Sn-Sn-1=1/2(根号Sn+根号Sn-1)
(根号Sn-根号Sn-1)(根号Sn+根号Sn-1)=Sn-Sn-1
根号Sn-根号Sn-1=1/2
根号Sn为等差数列 且根号S2=2 公差d=1/2
根号S10=根号S2+0.5*6=5
S10=25