已知函數(shù)f(x)=3x+2,數(shù)列{an}滿足:a1≠-1且an+1=f(an)(n∈N*),若數(shù)列{an+c}是等比數(shù)列,則常數(shù)c=_.
已知函數(shù)f(x)=3x+2,數(shù)列{an}滿足:a1≠-1且an+1=f(an)(n∈N*),若數(shù)列{an+c}是等比數(shù)列,則常數(shù)c=______.
優(yōu)質(zhì)解答
∵f(x)=3x+2,數(shù)列{a
n}滿足:a
1≠-1且a
n+1=f(a
n)(n∈N
*),
∴a
n+1=f(a
n)=3a
n+2,…①
又∵數(shù)列{a
n+c}是等比數(shù)列,
∴
=k,
整理,得a
n+1+c=a
nk+ck…②
比較①式和②式,得k=3,
從而ck-c=2,解得出c=1.
故答案為:1.
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