(3x²-x+1) dx = (4) 1. (B) = 1. a²z (8). z = x³y-3y² - xy +1, Əx² (A) 6xy². (B) 6x²y. (9). The total differential of z=xy+ is y (4) dz = (y + -—-)dx + (x − )dy. 1 X (C) dz = (y + x)dx + ( )dy.. y y² (C) 2/12. (C) 0. (D) 2. (D) 6xy. 1 (B) d= = (x =)dx + (y + -)dy. dz (D) dz = (y)dx + (x+dy.