A:surprising, surprised, surprised
B:surprised, surprising, surprised
C:surprised, surprising, surprising
D:surprised, surprised, surprising
按要求回答下列问题:
在超市购买食品时要重点关注
若函数y=f(x)是函数y=ax(a>0,a≠1)的反函数,且f(4)=-2,则f(x)=( )