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已知公差不为零的等差数列{an}与等比数列{bn}满足:a1=b1,a3=b3,a7=b5,那么( ) A.b11=a13 B.b11=a31 c.b11=a63 D.b63=a11请写出解释!!!!!!
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teacher2：解答：设等差数列的公差为d、等比数列的公比为q ， 则a3=a1+2d、b3=b1*q^2；a7=a1+6d、b5=b1*q^4 所以a1=b1、a1+2d=b1*q^2、a1+6d=b1*q^4 解得q^2=2 、a1=b1=2d 取n=2^k-1、m=2k-1 ...(2009-04-06 18:56)
