=n^2 cn tin
Sur-tin=n^2 cn a 1 = s 1 = 1
c=-1
(n-1)an-1-sn-1=(n-1)^2-(n-1)
nan-( n-1)an-1-[sn-sn-1]=
(n-1)an-(n-1)an-1 = 2(n-1)
an- an-1= 2
an = 1 (n-1)* 2 = 2n-1
Preguntas reales del examen de ingreso a la universidad de Youdao
nSn 1-nSn-sn=n^2 cn
=n^2 cn tin
Sur-tin=n^2 cn a 1 = s 1 = 1
c=-1
(n-1)an-1-sn-1=(n-1)^2-(n-1)
nan-( n-1)an-1-[sn-sn-1]=
(n-1)an-(n-1)an-1 = 2(n-1)
an- an-1= 2
an = 1 (n-1)* 2 = 2n-1