What the quadratic inequality of (x–4) (x–2) > 0

Answer 1

(x-4)(x-2) > 0

case 1:
x-4 > 0 AND x-2 > 0 , they are both positive
x > 4 AND x>2 ----> x > 4

case 2:
x-4 < 0 AND x-2 < 0 , they are both negative
x < 4 and x < 2 ----> x < 2

so :
x < 2 OR x > 4

Answer 2

or, using what you know about parabolas, since this one opens upward, the graph is below the x-axis between the roots (2<x<4)
so y>0 on the two intervals derived above.