AM/AE=AD/AN from Rt⊿ADM∽Rt⊿ANE, or AE=AM*AN/AD=AM? / 16=(8? +x? )/ 16,
He = DM = x from RT ⊿ FHE ≌ RT ⊿ ADM;
BF = AH = AE-HE; BF+AE=2AE-HE=(8? +x? )/8-x
The area of trapezoidal ABFE is S=AB*(BF+AE)/2=4(BF+AE)=(8? +x? )/2-4x=x? /2-4x+32。 ,
The area of trapezoidal CDEF y=AB? -S=64-(x? /2-4x+32)=-x? /2+4x+32 .