原式=2-xx(x-2)=-1x，
故答案为：-1x．
Paul is very proud ______ his father because he helps keep our city beautiful. [ ]
A. in
B. of
C. on
D. from
呼吸功能异常易引起的错位是（）
A．下颌后缩畸形
B．以上都是
C．单侧后牙反牙合
D．后牙锁牙合
E．佝偻病
