令3^2x=4^3y=12^6=K则log3(k)=2X,log4(k)=3y,log12(k)=6 (1)把（1）变形logk(3)=1/2X,logk(4)=1/3Y,logk(12)=1/6logk(3)+logk(4)=1/2x+1/3y即logk(12)=1/2x+1/3y=1/6 分子分母通分即(3y+2x)/6xy又因为：3/x+2/y=(3y+...