> 数学 >
已知
lim
n→∞
an2+cn
bn2+c
=2
lim
n→∞
bn+c
cn+a
=3
,则
lim
n→∞
an2+bn+c
cn2+an+b
=(  )
A.
1
6

B.
2
3

C.
3
2

D. 6
人气:349 ℃ 时间:2020-02-03 14:39:58
解答
lim
n→∞
an2+cn
bn2+c
=2
lim
n→∞
bn+c
cn+a
=3
,∴
a
b
=2,
b
c
=3,∴
a
c
=2×3=6. 
lim
n→∞
an2+bn+c
cn2+an+b
=
lim
n→∞
a +
b
n
+
c
n2
c+
a
n
+
b
n2
=
a+0+0
c+0+0
=
a
c
=6,
故选D.
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