(x - 2)*(x - 4)*(x - a) > 0
((x - 4)*(x - 2))*(-a + x) > 0
/ 2 \ 3 2 a*\-8 - x + 6*x/ > - x - 8*x + 6*x
a*(-x^2 + 6*x - 8) > -x^3 + 6*x^2 - 8*x