$\displaystyle \lim_{x \to a} \dfrac{\sqrt{2a^3x-x^4}-a\sqrt[3]{a^2x}}{a-\sqrt[4]{ax^3}}$

There aren't any steps for this on Wolfram so..

I have a question. I know that this limit is to find the derivative at a certain point, whereas $\displaystyle x \to 0$ is for any point. I must have forgotten how to evaluate this but.. How exactly do I do this? Can I use direct substitution? I'm not looking for the answer or for you to show me how you would do it, just where I start. Thanks!