b分之2根号下ab的五次方乘（-二分之三根号下a立方b)除以3根号下a分之b
=2/b*a²b²√(ab)*[-3/2a√(ab)]÷3/a√(ab)
=-3ab*ab÷3/a√ab
=-a³b/√ab
=-a²√(ab)