
设Sn是等差数列{An}的前n项和,若S3/S6=1/3,则S6/S12=???
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S3/S6=1/3
(3a1+3d)/(6a1+15d)=1/3
(a1+d)/(2a1+5d)=1/3
a1=2d
S6/S12=(6a1+15d)/(12a1+66d)=27d/(90d)=3/10
(3a1+3d)/(6a1+15d)=1/3
(a1+d)/(2a1+5d)=1/3
a1=2d
S6/S12=(6a1+15d)/(12a1+66d)=27d/(90d)=3/10
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