等差数列an,bn的前n项和为An,Bn,对一切自然数n都有An/Bn=7n+1/4n+27,an/bn=?

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等差数列an,bn的前n项和为An,Bn,对一切自然数n都有An/Bn=7n+1/4n+27,an/bn=?
等差数列an,bn的前n项和为An,Bn,对一切自然数n都有An/Bn=7n+1/4n+27,an/bn=?

等差数列an,bn的前n项和为An,Bn,对一切自然数n都有An/Bn=7n+1/4n+27,an/bn=?
等差数列有个性质：连续奇数项的和等于项数乘以中间项,
如 a2+a3+a4=3a3 ,a5+a6+a7+a8+a9= 5a7 ,a1+a2+a3+a4+a5+a6+a7=7a4 等；
因此有 S(2n-1)=(2n-1)*an .
an/bn=[(2n-1)an]/[(2n-1)bn]=A(2n-1)/B(2n-1)=[7(2n-1)+1]/[4(2n-1)+27]=(14n-6)/(8n+23) .

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