Not sure if this belongs in pre-calc or not but I guess it's better safe than sorry.

I'm trying to determine the values of x so that the tangent to the function $\displaystyle y=3/x^{(1/3)}$ is parallel to the line $\displaystyle x+16y+3=0$

What I did was set the derivative of the function equal to the slope of the line (which is 1), but I got a different answer than the book. Can anyone tell me if I'm doing anything wrong.

$\displaystyle 1=-1/x^{(4/3)}$