已知:如图,AB、BE、ED、CD依次相交于B、E、D,∠E=∠B+∠D.试说明AB∥CD.
(a2+1)2-4a2
5m(x-y)2+10n(y-x)3
-8ax2+16axy-8ay2
(a+b)2-9(a-b)2
-x5y3+x3y5