Question

已知等比数列{an}的公比为正数，且a3乘a9=2a5^2，a2=1.则a1=几谢谢了，大神帮忙啊

求详细过程解析

Answer 1

设公比 = q ,a2 = a1q = 1 a3 = a1q , a5 = a1q^4 ,a9 = a1q^8 a1q*a1q^8 = 2(a1q^4) a1^2*q^10 = 2a1^2*q^8 q = 2 又 公比为正数 所以，q = √2 因，a2 = a1q = 1 所以，a1 = 1/√2 = √2 / 2 请采纳

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