f(x)=log1/3(x^2-4x+31),令,Y=x^2-4x+31,有X属于R时,Y>0恒成立,Y的对称轴X=2.在对称轴的左边递减,对称轴的右边递增,而log1/3(y)为单调减函数,f(x)在区间(-无穷,2]上,单调递增,此时X=2时,f(x)有最大值,f(x)=log1/3(2^...