I'm pretty sure I'm making a small mistake on these problems. I've done several they way I'm sure it's done, and rechecked them and they always come back as incorrect.

Here's an example problem:

$\displaystyle r(u,v) = (-3u, 2u^2-4v, 5v^2)$ at the point (9, 6, 45)

From this I get that:

$\displaystyle (u,v) = (-3,3)$

$\displaystyle r_u = (-3,-12,0)$

$\displaystyle r_v = (0, -4, 30)$

I'm getting the answer:

$\displaystyle -360x - 90y + 12z + 3240 = 0$

How far off am I? I can post all my steps if needed.

Thanks.