A level maths - MPC4 (AQA) question off a paper, need help!?

Question

http://www.aqa.org.uk/qual/gceasa/qp-ms/AQA-MPC4-W-QP-JUN06.PDF

quetion 5a

i get 1-6x rather than y-6x
Any advice?

5bi!!!! sorry think i wrote the wrong q number

Answer 1

y^2-xy +3x^2 -5 = 0
When x = 1 we have
y^2 -y +3 - 5=0
y^2 -y -2=0
(y-2)(y+1)=0
So y= 2 or y = -1

2yy' -xy'-y +6x = 0
y'(2y -x) = y-6x
y' = (y-6x)/(2y-x)