EXERCISE 1.2. Obtain a partial differential equation from each of the following relations: (a) 2z = (ax + y) + b (b) ax + by + cz = 1 (c) z = (x + x-a)y + b (d) z = (x + a)(y - b) (e) f(xy + z) = x+y+z (f) f (z sin x, z cos y) = 0 (g) z = (y-ax) + 8(y-bx)