Partial Derivative

by Stevecgz
Tags: derivative, partial
 P: 68 Question: Let C be the trace of the paraboloid $$z=9-x^2-y^2$$ on the plane $$x=1$$. Find parametric equations of the tangent line L to C at the point P(1,2,4). What I did: $$z=8-y^2, x=1$$ $$f_{y}=-2y$$ $$f_{y}(1,2)=-4$$ So the parametric equations of L are: $$x=1$$ $$y=2+t$$ $$z=4-4t$$ Am I doing this correct? Thanks.