∵ quadrilateral ABCD is a rectangle, AF⊥AE.

∴∠DAB=∠ADC=∠ABF=∠EAF=90

∫≈ 1+∠BAE =∠2+∠BAE = 90

∴∠ 1=∠2

∠∠ADC =∠ABF = 90。

∴△ABF∽△ADE

(2) After passing through point M, enter MG⊥FC.

∵ quadrilateral ABCD is a rectangle with de = x.

∴AB=DC=4 ∴CE=4-x

∵MG⊥FC,∠C=90

∴MG∥CE

∴△FMG∽△FEC

M is the midpoint of EF.

∴EF:FM=2: 1

∴CE:MG=2: 1

∴MG= 1/2CE= 1/2(4-x)

I won't write it next. Very simple, I hope to adopt it.