31.已知函数f(x)=x+1xf(x)=x+\frac{1}{x}f(x)=x+x1,g(x)={2x,x<0log2x,x>0g(x)=\left\{\begin{array}{l}{{2}^{x},x<0}\\ {lo{g}_{2}x,x>0}\end{array}\right.g(x)={2x,x<0log2x,x>0,则((( )))