ghyang123 发表于 2012-6-3 20:36 
1,由斯勒茨基方程可得:dX1/dP1=dX1s/dP1-X1dX1m/dm
在方程两侧同时乘以P1/X1。可得(P1/X1)(dX1/dP1) ...
According to the Slutsky equation, there is the presumption in your "Es", that is the utility level holds constant, which is contradicted to the definition of Slutsky substitution. I think the answer should be
Es= -0.3-0.1x0.4=-0.34