由已知得a1+a3+a5=3a3=105,
a2+a4+a6=3a4=99,
∴a3=35,a4=33,∴d=a4-a3=-2.
∴a20=a3+17d=35+(-2)×17=1.
故选B
已知{an}为等差数列,a1+a3+a5=105,a2+a4+a6=99,则a20等于( ) A.-1 B.1 C.3 D.7
已知{an}为等差数列,a1+a3+a5=105,a2+a4+a6=99,则a20等于( )
A. -1
B. 1
C. 3
D. 7
A. -1
B. 1
C. 3
D. 7
数学人气:397 ℃时间:2019-12-13 01:36:12
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