log9(3x)=log3(3x)/log3(9)=[1+log3(x)]/2【log3（x）】平方+log9(3x)=2 【log3（x）】平方+[1+log3(x)]/2=2 2[log3(x)]^2+1+log3(x)=42[log3(x)]^2+log3(x)-3=0[2log3(x)+3][log3(x)-1]=0log3(x)=-3/2 或log3(x)=1x...