7. 等差数列{an}中.a1+a2+-+a50=200.a51+a52+-+a100=2700.则a1等于( ) A.-1221 B.-21.5 C.-20.5 D.-20 查看更多

 

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等差数列{an}中,a1+a2+…+a50=200,a51+a52+…+a100=2700,则a1等于(    )

A.-1221             B.-21.5                 C.-20.5                 D.-20

查看答案和解析>>

等差数列{an}中,a1+a2+…+a50=200,a51+a52+…+a100=2700,则a1等于

[  ]

A.-1221
B.-21.5
C.-20.5
D.-20

查看答案和解析>>

等差数列{an}中,a1+a2+…+a50=200,a51+a52+…+a100=2700则a1等于

[  ]

A.-1221

B.-21.5

C.-20.5

D.-20

查看答案和解析>>

等差数列{an}中,a1+a2+…a50=200,a51+a52+…a100=2700,则a1等于

[  ]

A.-1221

B.-21.5

C.-20.5

D.-20

查看答案和解析>>


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