Candidates performed creditably well in this question. In part (a) they were able to find dy/dx of x2 + 4xy – y2 = 7 as x + 2y , substitute -2 for x and 4 for y
y - 2x
to get dy/dx = ¾ or 0.75;
In part (b) candidates factorised the denominator x2 – 9x + 18 correctly to get (x – 6)(x-3), and got
x + 3 = A + B , multiply through by x2-9x +18 to get
x2-9+18 (x – 6) (x – 3)
From x + 3 = A(x-3) + B(x-6) they were able to determine the values of A and B as A = 3, B = -2.
