证:
b1=log2(a1+1)=log2(3+1)=log2(4)=2
a(n+1)=an²+2an
a(n+1)+1=an²+2an+1=(an+1)²
b(n+1)=log2[a(n+1)+1]=log2[(an+1)²]=2log2(an+1)=2bn
b(n+1)/bn=2,为定值.
数列{bn}是以2为首项,2为公比的等比数列.
证:
b1=log2(a1+1)=log2(3+1)=log2(4)=2
a(n+1)=an²+2an
a(n+1)+1=an²+2an+1=(an+1)²
b(n+1)=log2[a(n+1)+1]=log2[(an+1)²]=2log2(an+1)=2bn
b(n+1)/bn=2,为定值.
数列{bn}是以2为首项,2为公比的等比数列.