(n-1)=27bn
bn=b(n-1)/27
bn为首项为1/3,公比为1/27.bn=9/(27)^n.
an+logkbn=3n-7+logk *9/(27)^n=3n-7+logk *9-logk(27)^n=3n-7+logk *9-3nlogk3
an+logkbn为常数,logk3=1 k=3
(n-1)=27bn
bn=b(n-1)/27
bn为首项为1/3,公比为1/27.bn=9/(27)^n.
an+logkbn=3n-7+logk *9/(27)^n=3n-7+logk *9-logk(27)^n=3n-7+logk *9-3nlogk3
an+logkbn为常数,logk3=1 k=3