x2x-2+42-x
=x2x-2-4x-2
=(x+2)(x-2)x-2
=x+2．
故答案为：x+2．
Mozart started writing music ______________ he was four years old.
A until B after C before D when
烟草制品市场的特点有（）
A、多样性
B、适度性
C、复杂性
D、垄断性
