cn+(cn+1)=2n+3,c1=3求此数列前n项和
问题描述:
cn+(cn+1)=2n+3,c1=3求此数列前n项和
答
根据题意,2cn+1=2n+3,所以cn=n+1,c2=3,题目中c1=3,所以Sn=c1+S(n-1)(n》=2) =3+(c2+cn)/(n-1)(n》=2) =3+(3+n+1)/(n-1)(n》=2) =3+(4+n)/(n-1)(n》=2)