等差数列的公差为3,若a2,a4,a8成等比数列,求a4
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等差数列的公差为3,若a2,a4,a8成等比数列,求a4
![等差数列的公差为3,若a2,a4,a8成等比数列,求a4](/uploads/image/z/8279973-45-3.jpg?t=%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%E7%9A%84%E5%85%AC%E5%B7%AE%E4%B8%BA3%2C%E8%8B%A5a2%2Ca4%2Ca8%E6%88%90%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97%2C%E6%B1%82a4)
a2=a1+3,
a4=a1+9,
a8=a1+21
a4/a2=a8/a4
(a1+9)/(a1+3)=(a1+21)/(a1+9)
a1=3
a4=3+9=12
a4=a1+9,
a8=a1+21
a4/a2=a8/a4
(a1+9)/(a1+3)=(a1+21)/(a1+9)
a1=3
a4=3+9=12
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