I was wondering if I did the following problem right:

Write the equation of the plane tangent to the given surface at the given point P.

xyz+ 2x^3 - y^2 + z^2 = 10; P(2, -1, -1)

So what I did was find the gradient of the above and got:

<yz + 4x, xz - 2y, xy - 2z>

Substituting P in I got, a normal vector of <9, 0, 0>

This led to a plane equation of:

9(x - 2) = 0