Question 908625
{{{f(x) = x(x - 4)^8 - 3(x - 4)^9}}}
{{{f(x)=(x-4)^8(x-3(x-4))}}}
{{{f(x)=(x-4)^8(x-3x+12)}}}
{{{f(x)=(x-4)^8(12-2x)}}}
{{{f(x)=2(x-4)^8(6-x)}}}
The first term is always positive. 
The second term is negative when {{{x>6}}}