数列an中a1=1,a(n+1)=2an+3(n≥1),通项an=?,n、n+1为下标
问题描述:
数列an中a1=1,a(n+1)=2an+3(n≥1),通项an=?,n、n+1为下标
答
a(n+1)+3=2an+6
a(n+1)+3=2(an+3)
数列{an+3}为等比数列
an+3=(a1+3)*2^(n-1)
an+3=2^(n+1)
an=2^(n+1)-3