f(x^2)=f(x^2/x)+f(x)f(x^2)=2f(x)f(x)=f(x/1)+f(1)f(1)=0又f(3)=1,所以f(x)=log(3,x)f（x)+f(x-1/5)=log(3,x(x-1/5))要使f(x)+f(x-1/5)≥2,必要x(x-1/5)≥9x≥(1+sqrt(901))/10=3.1题目不全