96台南女中資優班成就測驗

修正一下

第 18 題
設直線 DE 交 AB 於 G，直線 BF 交 CD 於 H
AE^2 = DE * GE
GE = 9/4

令 CF = x，EF = 7 - x
AE/AF = GE/BF
BF = (3/4)(10 - x)

CF/CE = HF/DE
HF = (4/7)x

CF^2 = BF * HF
x^2 = (3/4)(10 - x) * (4/7)x
x = (3/4)(10 - x) * (4/7)
x = 3

BF = (3/4) * 7 = 21/4