因为2a>b>0
故：2a-b>0
故：a+4/[（2a-b）b]
= a+2/[（a-b/2）b]
= (a-b/2)+b/2+1/[（a-b/2）(b/2)]
≥3•{(a-b/2)•b/2•1/[（a-b/2）(b/2)]}^1/3=3
故：a+4/（2a-b）•b的最小值为3,此时a=b=2