由a²b>=0,b²/a>=0所以a>0,b>=0所以|a|=a,|b|=b原式=[a/b*2/(2/3)]*√[(a²b)*(b²/a) /(a³b)]=(3a/b)*√(ab³/a³b)=(3a/b)*√(ab³/a³b)=(3a/b)*√(b²/a²)=(3a/b)*√b²//√a²=(3a/b)*|b|/|a|=(3a/b)*b/a=3