Unlike direct utility function, the Indirect Utility Function takes price as the input.
本质上体现的是，我们研究不在意人具体消费了什么，而是通过改变 or to investigate how they would affect workers’ utility.
We usually formed by , which is also: subject to , and then we could use Lagrangian Multiplier to solve the maximization problem.
and the solution is then Marshallian Demand.