This question was also reported to be attempted by majority of the candidates and they performed well in it. Majority of the candidates who attempted this question were reported to have differentiated xy2 +x2y = 4xy implicitly to obtain   + y2 + x2 + 2xy = 4.  Simplifying and bringing like terms together gave = .  The required gradient at the point (1,3) was obtained by substituting 1 for x and 3 for y in the equation and simplifying.  This gave  =   = - 1.