设等比数列{An}的公比q=1/2,求S4/A4.
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设等比数列{An}的公比q=1/2,求S4/A4.设等比数列{An}的公比q=1/2,求S4/A4.设等比数列{An}的公比q=1/2,求S4/A4.设A1=A则A4=A1*1/8S4=A1*(1-1
设等比数列{An}的公比q=1/2,求S4/A4.
设等比数列{An}的公比q=1/2,求S4/A4.
设等比数列{An}的公比q=1/2,求S4/A4.
设A1=A
则A4=A1*1/8
S4= A1*(1-1/16) / (1-1/2)=15/8 A1
所以比值= 15/8* A1 / A1*1/8=15
15
S4=a1*(1-q^4)/(1-q)
=a1(1+q^2)(1-q^2)/(1-q)
=a1(1+q^2)(1-q)(1+q)/(1-q)
=a1(1+q^2)(1+q)
=a1(1+1/4)*3/2
=a1*5/4*3/2
=15a1/8
a4=a1q^3
=a1*1/8
=a1/8
S4/a4=(15a1/8)/(a1/8)=15
设等比数列{An}的公比q=1/2,求S4/A4.
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