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等差数列的前n项和为,且 =6,=4, 则公差d等于( )
A.1 B C.- 2 D 3
等差数列的前n项和为,且 =6,=4,则公差d等于( )
A.1 B. C.- 2 D.3
等差数列的前n项和为,且=6,=4, 则公差等于( )
A.3 B. C.1 D.-2
A.1 B. C.- 2 D.3
等差数列的前n项和为,且 =6,=4, 则公差d等于 ( )