Answer:
x < -4 or x > 7.
Step-by-step explanation:
We first determine the critical points by solving x^2 - 3x - 28 = 0:
x^2 - 3x - 28 = 0
(x - 7)(x + 4) = 0
x = 7, - 4
so the critical points are -4 and 7.
Create a Table (pos = positive and neg = negative):
Value of x< - 4 -4 < x < 7 x > 7
---------------------|----------- |--------------------- |---------------------
x + 4 NEG POS POS
x - 7 NEG NEG POS
(x + 4)(x - 7) POS NEG POS
So the function is positive (>0) for x < -4 or x > 7.
You can also do this by drawing the graph of the function.
