题目内容：

正方形abcd的边长为12cm,ce=2de.(1)求cef的面积(2)求df.

优质解答

∵CE=2DE
∴CE = 2/3 * 12 = 8 cm
(1)S(CEF) = S(BCF) - S(BCE)
= 1/2 * 12*12 - 1/2*12*8
= 24 cm²
(2) S(CEF) = 1/2*CE*DF
1/2 * 8 * DF = 24
DF = 6 cm