##### Hint

This one is tricky because your mind refuses to believe that $c$ is just a fixed number. Remember, since $c$ behaves just like a number, it does not depend on $y$. If it helps, try substituting your favorite number for $c$ to practice treating $c$ like a number when differentiating.

In particular, for the first term $c^2$, you have to resist the temptation of calculating the derivative as though you were differentiating with respect to $c$. If you were taking the derivative of $47^2$, you wouldn't say that the answer was $2 \cdot 47^1$, would you?

The expression $g'(1)$ means that you first calculate the derivative of $g(y)$ with respect to $y$, then substitute in $1$ for $y$. It doesn't mean you are supposed to do anything with the $c$.

Hide help