要素替代弹性 d(K/L d(MP:MPk) (K/L)(MP/MPk) =an(交y/dn(3 -dn(》/an(g》 =dn(交y/dn(经+ln(》( / ) ( / ) ( / ) ( / ) L K L K MP MP d MP MP K L d K L  = = = = + = d K L d MP MP d K L d K L d K L d K L L K (ln( )) (ln( )) (ln( )) (ln( )) (ln( )) (ln( ) ln( ))     1 要素替代弹性