log以1/2为底的（9的（x-1）次方-5）=log以1/2为底的[（3的（x-1）次方-2）/(1/2)^2]所以9^(x-1)-5=[3^(x-1)-2]/(1/4)令a=3^(x-1),则9^(x-1)=a^2a^2-5=4a-8a^2-4a+3=0a=1,a=33^(x-1)=1,x-1=0,x=13^(x-1)=3,x-1=1,x=2...