1. Find dz and then evaluate using the given information. (a) z = 2x3 + 3xy + y3, x = 2, y = 1, dx = 0.02, dy = 0.03 xty (b) z = -2 "x2+v2 , x = 1, y = 3, dx = -0.4, dy = 0.2 (c) z = In(x3 + y2) , x = 2, y = 4, dx = 0.2, dy = 0.15