Write a quadratic inequality that has the solution x(</=)4 or x(>/=)12

Answer 1

the vertex of a parabola lies midway between the roots. So you have
f(x) = a(x-8)^2 + k
If the parabola opens up, then y ≥ f(x)
if it opens down, then y ≤ f(x)
so finish it off