Finding the equation for a tangent line at a certain point I would like to find the equation for the tangent line of $y=(x^3-25x)^8$ at point $(-5,0)$.
I know that you have to find the first derivative, but I don't know where to go from there.

Once a value for the slope $m$ is known from the derivative at the given point, use the parameterized definition of a line to get values for x and y in terms of the parameter t and the tangent point (-5,0):
$x = 1 * t - 5$
$y = m * t + 0$  
If desired, eliminate t from this system of equations to obtain a standard equation fo the line just in terms of $x$ and $y$.
