Hi,

The question is: Find the eq. of the level surface through point p= (1,2,-1) and find the eq of the straight line in R3 which is normal to this surface at p

Is finding the equation of the level surface to f(x,y,z) = x^2 - y^2 + z^2 at point (-1,2,-1) the same as finding the equation of the tangent plane to the surface at that point?

Thanks for any help!