Dearing Ted : First, Thanks Your help last time!!! But I have an another question now!! If we want to solve following equation, how can i do first?? We want to solve X's and Y's value!! X,Y>0 When we have two equation: For example: exp(X)+(Y*Y)=exp(1)+4 (X*X)+2Y=5 Please help me!! And give me a reference to solve it!! THANK YOU!! Huang [[alternative HTML version deleted]]