①f(x+y)=f(x)•f(y)是正确的,因为f(x+y)=ax+y=ax×ay=f(x)•f(y); ②f(xy)=f(x)+f(y)是不正确的,因为f(xy)=axy≠ax+ay=f(x)+f(y); ③f(x-y)=是正确的,因为f(x-y)=ax-y==; ④f(nx)=fn(x)是正确的,因为f(nx)=anx=(ax)n=fn(x); ⑤f[(xy)n]=fn(x)•fn(y)是不正确的,因为f[(xy)n]=a(xy)n=axn×ayn≠(ax)n(ay)n=fn(x)•fn(y) 综上,不正确的是②⑤ 故答案为②⑤ |