数列{an}满足a1=1,an=2an-1-3n+6(n>=2,n∈N+)(1)设bn=an-3n,求证:数列{bn}是等比数列
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数列{an}满足a1=1,an=2an-1-3n+6(n>=2,n∈N+)(1)设bn=an-3n,求证:数列{bn}是等比数列数列{an}满足a1=1,an=2an-1-3n+6(n>=2,n∈N+
数列{an}满足a1=1,an=2an-1-3n+6(n>=2,n∈N+)(1)设bn=an-3n,求证:数列{bn}是等比数列
数列{an}满足a1=1,an=2an-1-3n+6(n>=2,n∈N+)(1)设bn=an-3n,求证:数列{bn}是等比数列
数列{an}满足a1=1,an=2an-1-3n+6(n>=2,n∈N+)(1)设bn=an-3n,求证:数列{bn}是等比数列
证:
n≥2时,
an=2a(n-1)-3n+6
an-3n=2a(n-1)-6(n-1)=2[a(n-1)-3(n-1)]
(an -3n)/[a(n-1)-3(n-1)]=2,为定值.
a1-3=1-3=-2,数列{an -3n}是以-2为首项,2为公比的等比数列.
bn=an-3n,数列{bn}是是以-2为首项,2为公比的等比数列.
傻逼
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