等差数列an、bn的前n项和分别为sn、tn,an/bn=2n+1/3n-2,求a11/b11和S2n+1/T2n+1

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等差数列an、bn的前n项和分别为sn、tn,an/bn=2n+1/3n-2,求a11/b11和S2n+1/T2n+1
等差数列an、bn的前n项和分别为sn、tn,an/bn=2n+1/3n-2,求a11/b11和S2n+1/T2n+1

等差数列an、bn的前n项和分别为sn、tn,an/bn=2n+1/3n-2,求a11/b11和S2n+1/T2n+1
设a11和b11为中项
则N为21代入得
S21比T21等于21乘以2加1比上3乘以21减2
答案为43/61

公式 S 2n-1 = (2n-1) A n

an/bn=2n+1/3n-2
=> a11/b11 = (2*11+1)/(3*11-2) = 23/31
设an=2n+1 则bn=3n-2
=> a1=3
Sn=n^2+2n
=> b1=1
Tn=(3n^2-n)/2
S2n+1/T2n+1 = [(2n+1)^2+2*(2n+1)]/{[3*(2n+1)^2-(2n+1)]/2}
= [8n^2+16n+6]/[12n^2+10n+2]

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