C4 binomial expansion help

I'm trying to do question 3b on this paper and have looked at the mark scheme but I can't understand what is supposed to happen to the 256 in the question as the answer seems to ignore it.
http://www.mathsgeeks.co.uk/allpapers/C4/C4AQAJan10QP.pdf
here is the mark scheme
http://www.mathsgeeks.co.uk/allpapers/C4/C4AQAJan10MS.pdf
i have found part a fine
i would appreciate it if anyone could help me get a better understanding of this, thanks

I'm trying to do question 3b on this paper and have looked at the mark scheme but I can't understand what is supposed to happen to the 256 in the question as the answer seems to ignore it.
http://www.mathsgeeks.co.uk/allpapers/C4/C4AQAJan10QP.pdf
here is the mark scheme
http://www.mathsgeeks.co.uk/allpapers/C4/C4AQAJan10MS.pdf
i have found part a fine
i would appreciate it if anyone could help me get a better understanding of this, thanks

Part b follows on from part a, in terms of content. So, we want to get our expression into a form similar to that of $\displaystyle\left(1+\frac{3}{4}x\right)^{-\frac{1}{3}}$

If we divide the top and bottom of our fraction under the cube root, we have:

$\displaystyle\sqrt[3]{\frac{256}{4+3x}}=\sqrt[3]{\frac{64}{1+\frac{3}{4}x}}=64^{\frac{1}{3}}\left(1+\frac{3}{4}x\right)^{-\frac{1}{3}}$

Giving us the "4" in front of the brackets in the MS.