两题高一简单的等比数列,求解已知等比数列a1+a2=3,a3+a4=12,则a2乘以a3 =已知等比数列a1=1,a10=3,则a2乘以a3乘以a4乘以a5乘以a6乘以a7乘以a8乘以a9=
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![两题高一简单的等比数列,求解已知等比数列a1+a2=3,a3+a4=12,则a2乘以a3 =已知等比数列a1=1,a10=3,则a2乘以a3乘以a4乘以a5乘以a6乘以a7乘以a8乘以a9=](/uploads/image/z/8035974-54-4.jpg?t=%E4%B8%A4%E9%A2%98%E9%AB%98%E4%B8%80%E7%AE%80%E5%8D%95%E7%9A%84%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97%2C%E6%B1%82%E8%A7%A3%E5%B7%B2%E7%9F%A5%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97a1%2Ba2%3D3%2Ca3%2Ba4%3D12%2C%E5%88%99a2%E4%B9%98%E4%BB%A5a3+%3D%E5%B7%B2%E7%9F%A5%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97a1%3D1%2Ca10%3D3%2C%E5%88%99a2%E4%B9%98%E4%BB%A5a3%E4%B9%98%E4%BB%A5a4%E4%B9%98%E4%BB%A5a5%E4%B9%98%E4%BB%A5a6%E4%B9%98%E4%BB%A5a7%E4%B9%98%E4%BB%A5a8%E4%B9%98%E4%BB%A5a9%3D)
两题高一简单的等比数列,求解已知等比数列a1+a2=3,a3+a4=12,则a2乘以a3 =已知等比数列a1=1,a10=3,则a2乘以a3乘以a4乘以a5乘以a6乘以a7乘以a8乘以a9=
两题高一简单的等比数列,求解
已知等比数列a1+a2=3,a3+a4=12,则a2乘以a3 =
已知等比数列a1=1,a10=3,则a2乘以a3乘以a4乘以a5乘以a6乘以a7乘以a8乘以a9=
两题高一简单的等比数列,求解已知等比数列a1+a2=3,a3+a4=12,则a2乘以a3 =已知等比数列a1=1,a10=3,则a2乘以a3乘以a4乘以a5乘以a6乘以a7乘以a8乘以a9=
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{1}:
因为{an}为等比,a1+a2=3,a3+a4=12
所以a1+a1*q=3,a1*q^2+a1*q^3=12,合并得3q^2=12,得q=±2,【1】q=2得a1=1,则a2*a3=8【2】q=-2得a1=-3,则a2*a3=-72
{2}:
因为为等比,
所以a2*a3*a4*a5*a6*a7*a8*a9=(a1)^9*(q^9)^4
因为a1=1,a10=3,则q^9=3,将其代入,所以值为81