Fce真题4

ADF面积=1/2 AD*DF

ECF地区=1/2 CE*CF

CE:AD=CF:(CD-CF)

CE=AD*CF/(CD-CF)

1/2 AD *(CD-CF)-1/2 CE * CF = 4

解是CE = 9，DF/CF=8/9，DF+CF= 17/9 CF = 8。

CF=72/17

DF= 64/17

AD*DF = 8 * 64/17

CE*CF = 9*72/17

CE * CF-AD * DF =(9 * 72-8 * 64)/17 = 8