Question 740662
You made a small mistake somewhere.  


{{{ 2x^2(x^2-4)-x(x^2-4)+(4-x^2)}}}
= {{{2x^2(x^2-4)-x(x^2-4)-(x^2-4)}}}
={{{(x^2-4)(2x^2-x-1)}}}


Factor the TRINOMIAL into {{{(2x+1)(x-1)}}}.


The fully factored polynomial is {{{highlight((x-2)(x+2)(2x+1)(x-1))}}}.
Notice just the change in "sign" or into "addition" for 2x+1.