2х(х+3)(7-х) меньше или равно 0

2x(x + 3)(7 - x) ≤ 0
- 2x(x + 3)(x - 7) ≤ 0
x(x + 3)(x - 7) ≥ 0
       -                 +                 -                    +
_____________________________________
               - 3               0                    7
                //////////////////                      /////////////////////
x ∈ [- 3 ; 0] ∪ [7 ; + ∞)