Derivative question

[Caligar]

Alright, I have a question. I've been working on this question with a friend for over an hour, and simply cannot get it.

 

"A curve is parametrized by the equations x=square-root t, and y=(t-3)^2. Find an equation of the line tangent to the curve at the point defined by t=9"

I know the answer is y=72x-180, because it is a study sheet, not actual homeowork. However, I need to understand how to do it for obvious reasons. Any help would be appreciated

 

 

EDIT: Gaah, got it. We were taking the first derivative at the wrong time

Delete please, Admins

Edited December 19, 2008 by Caligar