(an)为等比数列,且前三项和为168,a2-a5等于4的2次方,则a5与a7的等比中项为多少?
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![(an)为等比数列,且前三项和为168,a2-a5等于4的2次方,则a5与a7的等比中项为多少?](/uploads/image/z/5457299-59-9.jpg?t=%28an%29%E4%B8%BA%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97%2C%E4%B8%94%E5%89%8D%E4%B8%89%E9%A1%B9%E5%92%8C%E4%B8%BA168%2Ca2-a5%E7%AD%89%E4%BA%8E4%E7%9A%842%E6%AC%A1%E6%96%B9%2C%E5%88%99a5%E4%B8%8Ea7%E7%9A%84%E7%AD%89%E6%AF%94%E4%B8%AD%E9%A1%B9%E4%B8%BA%E5%A4%9A%E5%B0%91%3F)
(an)为等比数列,且前三项和为168,a2-a5等于4的2次方,则a5与a7的等比中项为多少?
(an)为等比数列,且前三项和为168,a2-a5等于4的2次方,则a5与a7的等比中项为多少?
(an)为等比数列,且前三项和为168,a2-a5等于4的2次方,则a5与a7的等比中项为多少?
a1+a1q+a1q^2=168
a2-a5=16-----a1q-a1q^4=16 q