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信息發(fā)布者：
?$ \frac {EF}{FG}$?
?$ \frac {AD}{BD}$?
12
2：3
6
?$ 證明：∵?EG//BC?$?
?$∴?\frac {AE}{AB}=\frac {AG}{AC}?$?
?$∵?GF//CD?$?
?$∴?\frac {AF}{AD}=\frac {AG}{AC}?$?
?$∴?\frac {AE}{AB}=\frac {AF}{AD}?$?
1
?$解：過(guò)點(diǎn)?D?作?DF//BE，?交?AC?于點(diǎn)?F?$?
?$∵?DF//BE?$?
?$∴?\frac {CF}{CE}=\frac {CD}{BC}=\frac {1}{2}?$?
?$∴點(diǎn)?F ?為?CE?的中點(diǎn)$?
?$∵?DF//BE$?
?$∴?\frac {AO}{AD}=\frac {AE}{AF}?$?
?$? (1)?∵?\frac {AE}{AC}=\frac {1}{2}?$?
?$∴?\frac {AE}{AF}=\frac {2}{3}?$?
?$∴?\frac {AO}{AD}=\frac {2}{3}?$?
?$? (2)?∵?\frac {AE}{AC}=\frac {1}{3}?$?
?$∴?\frac {AE}{AF}=\frac {1}{2}?$?
?$∴?\frac {AO}{AD}=\frac {1}{2}?$?
?$? (3)?∵?\frac {AE}{AC}=\frac {1}{4}?$?
?$∴?\frac {AE}{AF}=\frac {2}{5}?$?
?$∴?\frac {AO}{AD}=\frac {2}{5}?$?
?$? (4)?∵?\frac {AE}{AC}=\frac {1}{n+1}?$?
?$∴?\frac {AE}{AF}=\frac {2}{n+2}?$?
?$∴?\frac {AO}{AD}=\frac {2}{n+2}?$?
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