2(2/a+1/3b)
=(3a+2b)(2/a+1/3b)
=6+a/b+4b/a+2/3
=20/3+(a/b+4b/a)
a/b+4b/a≥2√(a/b*4b/a)=4
则2(2/a+1/3b)≥20/3+4=32/3
2/a+1/3b≥16/3
最小值是16/3