For (x^3)z + (z^3)x - 2yz = 0, find the equation of the tangent plane to the surface at (1,1,1). I'm not quite sure how to start this problem.
Okay, start by finding the gradient of the function f(x,y,z)= $\displaystyle x^3z+ z^3x- 2yz$. That vector, evaluated at (1, 1, 1), will be perpendicular to the tangent plane.