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已知等差数列{an},{bn}的前n项的和分别为Sn,Tn,若对于任意的自然数n,都有Sn/Tn=2n-3/4n-3,则（a9/b5+b7）+（a3/b4+b8）=
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已知等差数列{an },{bn }的前n项的和分别为Sn,Tn,若对于任意的自然数n,都有Sn/T
n=2n-3/4n-3,则（a9/b5+b7）+（a3/b4+b8）=
n=2n-3/4n-3,则（a9/b5+b7）+（a3/b4+b8）=
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参考吧
a9/(b5+b7)+a3/(b8+b4)
=a9/2b6+a3/2b6
=a9+a3/2b6
=2a6/2b6
=(a1+a11)/(b1+b11)
=11(a1+a11)/11(b1+b11)
=[11(a1+a11)/2]/[11(b1+b11)/2]
=S11/T11
=19/41
a9/(b5+b7)+a3/(b8+b4)
=a9/2b6+a3/2b6
=a9+a3/2b6
=2a6/2b6
=(a1+a11)/(b1+b11)
=11(a1+a11)/11(b1+b11)
=[11(a1+a11)/2]/[11(b1+b11)/2]
=S11/T11
=19/41
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