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已知{an}为等差数列,a1+a3+a5=105,a2+a4+a6=99,则a2...
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
考点分析:
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、
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|=|
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与
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=( )
A.
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C.
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D.2
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D.
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等于( )
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B.1-2i
C.2+i
D.2-i
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