The gradient of the curve is given by the derivative \(\frac{dy}{dx}\) Given that y = x\(^3\) + 3x\(^2\) − 9x + 5 \(\frac{dy}{dx}\) = 3x\(^2\) + 6x - 9 = 0 3x\(^2\) + 6x - 9 = 0 Divide through by 3 x\(^2\) + 2x - 3 = 0 Factorise x\(^2\) + 3x - x - 3 = 0 x(x + 3) - 1(x + 3) = 0 (x - 1)(x + 3) = 0 x = 1 Or x = -3 Therefore, x = -3 and x = -1