MAT-2130 Midterm: MATH 2130 App State Fall2012 Test2
Document Summary
Answer key: 10 points) let f (x, y) = x2 + 4y2. Be sure to show your work! (a) write down a general equation for the level curves / surfaces of f (circle the correct term). Answer: x2 + 4y2 = c (where c is some constant). For c > 0 these are ellipses (centered at the origin). For c = 0 this is just the origin itself. For c < 0 the level curves are empty. (b) write down the equation of the trace of z = x2 + 4y2 in the xz-plane. The equation for the xz-plane is y = 0. So the trace is z = x2 + 4(02). Answer: z = x2 (c) make a rough sketch of z = x2 + 4y2: (10 points) consider x and y as independent variables and z as a dependent variable where 5x + xy2 + ze3x+y = 10. Using the formulas for implicit di erentiation, compute both and.