x>0,y>0.log3(x+y)＝1→x+y＝3.∴1/x+9/y≥(1+3)^2/(x+y)＝16/3.∴log1/3(1/x+9/y)≤log1/3(16/3)＝log3(3/16).所求最大值为：log3(3/16).
