Wolfram Derivation Error I'm trying to derive the equation 

$$y = (2x-6)^4$$

I thought that it would be

$$\frac{dy}{dx} = 8(2x-6)^3$$

Wolframalpha says $dy/dx = 64(x-3)^3$

Who's correct? I thought it would be a simple calc-1 chain rule.
$$\dfrac{dy}{dx}=8(2x-6)^3=8(2(x-3))^3=8\cdot(2^3(x-3)^3)=64(x-3)^3$$

As demostrated above, from the result you obtained to that obtained by Wolfram Alpha. As you can see, they are both equal.
There is no error. There is a common fact of $2$ in $(2x-6)$. That means we can write
\begin{eqnarray*}
(2x-6)^4 &amp;\equiv&amp; \left[2(x-3)\right]^4 \\ \\
&amp;\equiv&amp; 2^4\cdot(x-3)^4 \\ \\
&amp;\equiv&amp; 16(x-3)^4
\end{eqnarray*}
If you differentiate this then you will get what $64(x-3)^3$ as Wolfram Alpha gives you.

Alternatively, if you differentiate first then you have
\begin{eqnarray*}
8(2x-6)^3 &amp;\equiv&amp; 8\left[2(x-3)\right]^3 \\ \\
&amp;\equiv&amp; 8\cdot 2^3\cdot(x-3)^3 \\ \\
&amp;\equiv&amp; 64(x-3)^3
\end{eqnarray*}