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等差数列.sn/tn=n+1/2n-1则a9/b10=?
题目详情
等差数列.sn/tn=n+1/2n-1则 a9/b10=?
▼优质解答
答案和解析
设an=a1+(n-1)d1,bn=b1+(n-1)d2
S1/T1=2
a1/b1=2 a1=2b1
S2/T2=1
S2=T2
a1+a1+d1=b1+b1+d2
d1=d2-2b1
S3/T3=4/5
5(3a1+3d1)=4(3b1+3d1)
10b1+5d1=4b1+4d1
d1=-6b1
d2=d1+2b1=-4b1
a9/b10=(a1+8d1)/(b1+9d2)
=(2b1-48b1)/(b1-36b1)
=(-46b1)/(-35b1)
=46/35
S1/T1=2
a1/b1=2 a1=2b1
S2/T2=1
S2=T2
a1+a1+d1=b1+b1+d2
d1=d2-2b1
S3/T3=4/5
5(3a1+3d1)=4(3b1+3d1)
10b1+5d1=4b1+4d1
d1=-6b1
d2=d1+2b1=-4b1
a9/b10=(a1+8d1)/(b1+9d2)
=(2b1-48b1)/(b1-36b1)
=(-46b1)/(-35b1)
=46/35
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