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Let

\displaystyle {f{{\left({x}\right)}}}=-{4}{\ln{{\left({8}{x}\right)}}}

\displaystyle {f}'{\left({x}\right)}=

\displaystyle {f}'{\left({4}\right)}=

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\displaystyle

Enter your answer as an expression. Example: 3x^2+1, x/5, (a+b)/c
Be sure your variables match those in the question

Enter your answer as a number (like 5, -3, 2.2172) or as a calculation (like 5/3, 2^3, 5+4)
Enter DNE for Does Not Exist, oo for Infinity