在數(shù)列{an}中,a1=2,an+1=an+ln(1+1n),則an=( ?。?A.2+lnn B.2+( n-1 ) lnn C.2+nlnn D.1+n+lnn
在數(shù)列{a
n}中,a
1=2,a
n+1=a
n+ln(1+
),則a
n=( ?。?br/>A. 2+lnn
B. 2+( n-1 ) lnn
C. 2+nlnn
D. 1+n+lnn
優(yōu)質(zhì)解答
∵在數(shù)列{a
n}中,a
1=2,a
n+1=a
n+ln(1+
),∴
an+1?an=ln.
∴a
n=(a
n-a
n-1)+(a
n-1-a
n-2)+…+(a
2-a
1)+a
1=
ln+ln+…+
ln+2
=
ln(??…?)+2=lnn+2.
故選A.
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