Lagrange Multipliers

I am just looking into this topic and if anyone know any good websites please let me know. perferably a site that have a bunch of excercise problems and solutions or answers.

btw my only source is google/yahoo and so far these sites arent as good as i'd like them to be.

also a question, what happens when there are more than one constraint?? i cant find any such examples on the net and all the theories for multi-variate arent helping.

Have you ever visited Mathworld ? There are 153 hits when you enter "lagrange".

is there a way when doing lagrange multipliers to deal with x>0, y>0, z>0??

i am thinking of replacing all x with a^2, y with b^2, c with c^2, would that work??