已知 a = 2 , 1 , b = 2 , - 1 , c = 0 , 1 , 则 a + b ⋅ c = ; a ⋅ b = .
的结果为 .
设函数定义如下表,数列满足且,则 .
已知等比数列中,为的两个根,则 .