' The two points on the curve x^2 + y^2 -xy = 84 where the gradient of the curve is 1/3 are A and B. Find the equations of the the tangents at A and B. '
I differentiated the equation to get what I think is correct : 2x + 2ydy/dx -xdy/dx -y = 0 .
It's just from here I seem to have no clue what to do, I make it equal to 1/3 but it doesn't seem to work out for me.
Any help is really appreciated so thank you