Answer:
c) (-∞, -4] or [7,∞)
Step-by-step explanation:
x² - 3x - 28 ≥ 0
x² - 7x + 4x -28 ≥ 0
x (x - 7) + 4(x - 7) ≥ 0
(x-7) (x + 4) ≥ 0
When x value lies in (-∞, -4], (x-7) value will be negative and (x+ 4) will be negative. So, result will be positive
When x value lies in [7,∞), both (x-7) and (x+ 4) will be positive. So, result will be positive
