8
By AAA similarity, △AEC ∼ △DEC: AB / DC = AE / DE = BE / CE = 2 / 1 Let: DE = x cm, CE = y cm The perimeter of △AEB: Perimeter = AB + AE + BE = 2 + 2x + 2y = 2 + 2(x + y) From the trapezium ABCD: AD + BC = 3 ⇒ x + y = 3 Substitute: Perimeter of △AEB = 2 + 2(3) = 8 cm