(a分之2b)的平方÷（a分之-b）×（-4a分之3b）的立方
=(2b/a)²÷（-b/a)×(-3b/4a)³
=(2b/a)²×（a/b)×(3b/4a)³
=(2b/a)×(3b/4a)³
=(54b^4)/(64a^4)
=(27b^4)/(32a^4)