Question 1142468
What you have or ask is not clear.


{{{h(x)=(6-3x)^3-4(6-3x)^2+7(6-3x)-1}}}
?


Then you ask for f(x)?

Just guessing, you have h(x) is composed of two functions, maybe using f(x) as input into some other function.  Very likely wanted is  {{{f(x)=6-3x}}}
and the other function might be some g,  {{{g(x)=x^3-4x^2+7x-1}}}.