用数学归纳法证明：当n=1时,ln((1+2)/2)=ln(3/2)=1）不等式成立,即ln((k+2)/2)={[(k+2)/(k+1)]^(k+1)}^[1/(k+1)]=(k+2)/(k+1)=1+1/(k+1)>1+1/(k+2)
=(k+3)/(k+2)
所以当n=k+1（k>=1）时,(k+3)/2