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#15fa080b-23f4-4367-ba4f-1fbe038949b9基础填空题等差数列的概念与通项数列

4.已知等差数列{an}\{a_{n}\},记SnS_{n}为数列{an}\{a_{n}\}的前nn项和,若a1=1a_{1}=1S7=5a5S_{7}=5a_{5},则数列{an}\{a_{n}\}的公差d=(d=(  ))