Find the slope of x^2-16xy+y^2=1 at (1,1).

Is this -1?

2x - 16y - 16xy' + 2yy' = 0

at (1,1)
2-16-16y'+2y' = 0
y' = 14/-14 = -1

you are correct. However, (1,1) is not on the graph. ??