lg(2^x)+lg(8^y)=lg2,
x*lg2+lg(2^(3y)=lg2,
x*lg2+3y*lg2=lg2,
(x+3y)lg2=lg2,
x+3y=1,
1/x+1/(3y)
=(1/x+1/(3y)*1
=(1/x+1/(3y)*(x+3y)
=1+x/(3y)+3y/x+1
=2+[x/(3y)+3y/x]
≥2+2√[x/(3y)*3y/x]
=2+2√1
=4.
因此最小值是4.