来自《耶鲁大学开放课程：金融理论 第2集 第2集》

• 
  
  or that's what she does, that's what he does.
  或者说这里是她的 那里是他的
• 
  
  And now the fifth one
  第五个
• 
  
  so now we have the two mysterious equations that are left.
  我们得到了左边两个神秘的等式**翻译可能不准确
• 
  
  So how do we express the idea
  我们如何表达这个观点
• 
  
  that the choices X_i and Y_i by i, that's her
  选择xi和yi 这是她
• 
  
  and she's going to optimize by choosing here somewhere.
  她想通过在这里选择来实现最优
• 
  
  This is her indifference curve, right, looked like that.
  看这里 这是她的无差异曲线
• 
  
  So that's what she's going to do.
  这是她要做的
• 
  
  And remember he's going to choose here.
  她要选择这里
• 
  
  So how can you turn her choice and his choice into an equation?
  怎样把他们的选择变成等式呢
• 
  
  Well, this was invented by a German guy Gossen in 1851
  1851年戈森提出了边际效用递减
• 
  
  and then rediscovered by Jevons, Menger and Walras,
  杰文斯 门格尔 瓦尔拉斯重新使用了它