7. (a) Find the total differential of z = f(x, y) = Vx2 + 2 and compute it's value when (x, y) = (3, -4) and (dr, dy) = (0.02, 0.01). (b) Find the total differential of f(x, y) = In(2x + y +2) and compute it's value when (x, y) = (0, 0) and (dx, dy) = (0.3, -0.2). 8. Using the total differentials to approximate V(4.96)2 + (12.06)2