f(lga)=a^(lga-1/2)=√10
取对数
lg[a^(lga-1/2)]=lg10^(1/2)
(lga-1/2)lga=1/2
2(lga)²-lga-1=0
(lga-1)(2lga+1)=0
lga=1,lga=-1/2
所以a=10,a=√10/10