解答：∵1/4>0∴ f(1/4)=log以2为底1/4的对数=-2∵ -2<0∴ f[f(1/4)]=f(-2)=3^(-2)=1/3²=1/9
f(1/4)=log2(1/4)=-2f(-2)=3^(-2)=1/9 f[f(1/4)]=1/9
f(1/4)=㏒2¼=-2f[f(1/4)]=f(-2)=3的-2次方=1/9
