I'm given:

If f(x) = $\displaystyle \frac{1}{x} - \frac{x}{4}$, then what is f($\displaystyle \frac{1}{4x})$

what's the procedure for solving this? For f($\displaystyle \frac{1}{4x})$, do I just divide 1 by 4 times $\displaystyle \frac{1}{x} - \frac{x}{4}$ ? I tried doing that and got the answer $\displaystyle \frac{x}{(2-x)(2+x)}$, but apparently that's not the answer. Can anyone work through this to show me the different stages of it?