已知数列｛an｝中a1=1且n大于1时,2sn的平方=2ansn-an求an

2sn^2=2ansn-an
2sn^2=2[sn-s(n-1)]sn-[sn-s(n-1)]
2sn^2=2sn^2-2sns(n-1)-sn+s(n-1)
2sns(n-1)+sn-s(n-1)=0
1/sn-1/s(n-1)=2
1/sn=1/s1+2(n-1)=2n-1
sn=1/(2n-1)
an=sn-s(n-1)=1/(2n-1)-1/(2n-3),
a1=1,an=1/(2n-1)-1/(2n-3),