Determine all critical points for the following function.

f left parenthesis x right parenthesis equals $3$ x left parenthesis $16$ minus x right parenthesis cubedf$($x$)=3$x$(16$x$)3$

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Part $1$

What is the derivative of

f left parenthesis x right parenthesis equals $3$ x left parenthesis $16$ minus x right parenthesis cubedf$($x$)=3$x$(16$x$)3?$

f primef$($x$)$equals$=$enter your response here