Hello: I have already found references "optim" , but I do not understand its means !! So I want to ask next question I have a question in Math. If we want to get X's and Y's solution, X>0 and Y>0 We have two equation : 2*exp(X)+X^2+3*Y=2*exp(1)+4 3*exp(X/Y)+3*X*Y+4*Y=3*exp(1)+7 How I use R-project to solve above question?? THANKS YOU !!!! THANK YOU VERY MUCH!! HLC [[alternative HTML version deleted]]