use distributie property which is
a(b+c)=ab+ac
therefor
6x(x-4)=6x^2-24x
distribute the negative 1 infroont of the (9x-1)
-1(9x-1)=-9x+1
now we have
6x^2-24x-16x^2-9x+1
gropu like terms
6x^2-16x^2-24x-9x+1
add like terms
-10x^2-33x+1 is simplest form