I have to differentiate this using the compsite rule only:
I am using k'(x)=g'(f(x)) f'(x)
where k(x)=g(f(x)) and
u = f(x) = x(4-x)/6 ,which I multiplied out to give 2/3x - 1/6x^2
so, f'(x) =2/3 - 2/3x
so, k'(x) = (e^u) (2/3 - 2/3x)
stuck from there, also not sure if all of the above is right. Help please.