解方程 log9(x)-3logx^2(3)=1

运用换底公式,变成以3为底的对数.
log3(x)/log3(9)-3*log3(3)/log3(x^2)=1
log3(x) /2- 3/2log3(x) =1
[log3(x)]^2 -3 =2log3(x)
令a=log3(x)
a^2-3=2a a^2-2a-3=0
a=-1 or a=3
log3(x)=-1 或 3
x=3^(-1)=1/3 或x=3^3=27.