Theorem: For any real number $x,x^2-4vvxvv+160$

In a proof by cases of the theorem, there are three cases. The first case is that $x4.$

The second case is that $x-4.$ What is the third case?

a

$d.-4>ix>4-4$

$b.x<mn\; id="EditorElement\_283042">4</mn>$

$c.-4$

$d.-4>ix>4$