1. The problem statement, all variables and given/known data Here's the link (I scanned my homework), since it's hard to type the entire question on here, considering the mathematics-related symbols. I just want to make sure you all understand what I am asking. http://i1056.photobucket.com/albums/...ash5dash55.png [Broken] 2. Relevant equations f(x,y)= 3x^2 + 7y^2 3. The attempt at a solution What I did was derive the function f(x,y)= 3x^2 + 7y^2, which resulted in the answer E_1= 6 delta x, E_2= 14 delta y. However, the answer was declared wrong. I do not know what I did wrong. Was I supposed to derive the function? Could you please help explain this to me? Could you give me an example related to this problem? Please do what you are allowed to do to help me. I understand the need to figure things out for myself. Thank you so much!