_y1.請寫出

  a) CD效用函數與兩種財貨之需求函數

     ANS：

            U = X₁^a₁ + X₂^a₂  ,   X₁ = (a₁·m) / ((a₁+a₂) P₁)

                                       X₂ = (a₂·m) / ((a₁+a₂) P₂)

  b) 完全替代 u = ax+by 的所有需求函數

     ANS：

             a/p_x > b/p_y  → x = m/p_x , y = 0

             a/p_x < b/p_y  → x = 0 , y = m/p_y

             a/p_x = b/p_y  → 0 ≤ x ≤ m/p_x  , y = (m-p_x x)/p_y

  c) x與y以3:5比例的完全互補效用函數與所有需求函數

    ANS：

           U = min{x/3 , y/5}  ,  x = 3·m/(3p_x+5p_y)

                                          y = 5·m/(3p_x+5p_y)

  d) u = x + 2 √y , p_x = 1 , p_y = 5 , m =10

      求最適商品組

    ANS：

              MU₁/p₁= MU₂/p₂

              1/1 = (1/√y)/5

              √y = 1/5  ,  y = 1/25  ,  p_y·y = 1/5

              (m-p_yy)/p_x = 10 - 1/5 = 49/5

              x = 49/5 = 9.8