f(x)=a^(x-1/2), f(lga)=a^(lga-1/2)=a^lga/a^1/2=10^1/2 a^lga=(10a)^1/2 两边取lg lga*lga=1/2+1/2lga (lga)^2-1/2lga-1/2=0 (lga-1)(lga+1/2)=0 lga=1 a=10 lga=-1/2 a=10^(-1/2)=-√10/10
