A={0,4}
①当x=0时,解得a=1或-1
②当x=4时,解得a=7或1,然而a=7时,代入原题得B＝｛4,12｝,不符,舍去．
③B为空集,x无解,则a<-1
所以,a的范围为(-无穷,-1]并上{1}