序列专题
Sn=n^2*1/an
s(n+1)=(n+1)^2*1/a(n+1)
减去这两个表达式
a(n+1)/an=n/(n+2)
an = an/a(n-1)* a(n-1)/a(n-2)*...*a2/a1*a1=1/(2n^2+2n)
limsn=lim(n^2*an)=lim(n^2/(2n^2+n))=1/2
s(n+1)=(n+1)^2*1/a(n+1)
减去这两个表达式
a(n+1)/an=n/(n+2)
an = an/a(n-1)* a(n-1)/a(n-2)*...*a2/a1*a1=1/(2n^2+2n)
limsn=lim(n^2*an)=lim(n^2/(2n^2+n))=1/2