Hey folks. I have some more or less qualitative questions regarding optimization problems via Lagrange multipliers. I am following the http://en.wikipedia.org/wiki/Lagrange_multipliers" [Broken] on this one and I am just a little confused by their wording. In the first section titled "Introduction," they have the following: 1) My first question (which might seem silly) is: What is g(x,y) ? Is it a line? Or a surface? It looks like a line in their picture but I am used to functions of the forms g(x,y) being representative of surfaces; though I feel like it could be ambiguous. 2) Second, when they say: "Suppose we walk along the contour line with g = c." They don't mean that g = c IS the contour line right? They are saying that AT g(x,y) one can follow a contour line. It just seems like if g(x,y) = c is not a surface, then the whole idea of a contour is a little weird to me. So perhaps if someone can answer my first question this would make more sense to me. Sorry if these seem stupid, but it has been awhile.