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一、选择题1.设某等差数列的首项为a(a≠0),第二项为b,则这个数列中有一项为0的充要条件是( ).
First, multiple-choice questions 1. Let the first item of an arithmetic progression be a (a ≠ 0), and the second term be b. The necessary and sufficient condition for a zero in this sequence is ().