∵AB∥CD
∴∠DAE=∠F,∠D=∠FCE
∵AE平分∠BAD
∴∠BAE=∠DAE
∴∠BAE=∠F
∴AB=BF
∵BE平分∠ABC
∴∠ABE=∠CBE
∴△ABE≌△FBE (ASA)
∴AE=EF
∴△ADE≌△FCE (AAS)
∴CF=AD
∵BF=CF+BC
∴BF=AD+BC
∴AB=AD+BC
∵AB∥CD
∴∠DAE=∠F,∠D=∠FCE
∵AE平分∠BAD
∴∠BAE=∠DAE
∴∠BAE=∠F
∴AB=BF
∵BE平分∠ABC
∴∠ABE=∠CBE
∴△ABE≌△FBE (ASA)
∴AE=EF
∴△ADE≌△FCE (AAS)
∴CF=AD
∵BF=CF+BC
∴BF=AD+BC
∴AB=AD+BC