(a) If zy + ev = e where y = f(x), find the value of y" at the point where x = 0. (b) The product rule of differentiation is given as [9 marks] du =U du dx da + v dr (uv). where the two functions u(r) and v(r) are differentiable. (i) Derive the formula for the derivative of the product of three differentiable functions, say u(x), v(x) and w(x). [6 marks] (ii) Derive the formula for the derivative of the product of four differentiable functions of x, say u₁(x), u₂(x), u3(x) and u₁(x). [6 marks] (iii) What is the formula for the derivative of a finite number n of differentiable functions, (4 marks] say u₁(r). u₂(x), us(r)..... un(r).