ahqing88 发表于 2014-8-26 05:44 PM 
如果是ED = 4,那AF是多少?
EFD的面积是? ABF的面积又是?
资料 : EFD = ABF+10 , ABF=AF , AF =10-FD
From EFD= ABF+10 ,
(1/2)( ED)(FD) = AF+10
(1/2)(4)(FD) = (10-FD) + 10
2FD =20-FD
3FD = 20
FD=20/3
Sub FD= 20/3 into AF=10-FD ,
AF= 10-20/3
AF= 10/3
Since ABF=AF
ABF=10/3
Sub ABF = 10/3 into EFD=ABF+10
EFD =10/3 + 10
EFD= 40/3