Solve the inequality and select the solution set in interval notation: x2 - 2x - 8 > 0?

Question

A. (-∞, -2) U (4, ∞)
B. (-∞, -4) U (2, ∞)
C. (-2, 4)
D. No solutions

Answer 1

x^2-2x-8 is factored as (x-4)(x+2).

So that means that +4 and -2 are your boundary points.

Without checking specific points it looks like your answer would be A, but you have to check points in each of the intervals.

If you pick -10 for x, (-10)^2 - 2(-10) - 8 > 0
100 + 20 - 8 > 0
112 > 0 True so that means that the interval from negative infinity to -2 works.

If you pick 0 for x, (0)^2 - 2(0) -8 >0
0 - 0 - 8 > 0
-8 > 0 False

If you pick +10 for x, (+10)^2 - 2(+10) - 8 > 0
100 - 20 - 8 > 0
72 > 0 True so that means the interval from 4 to positive infinity works.

So after all that work and checking answer A seems to be the correct one.

Hope this helps. Good Luck. :)

Answer 2

if your looking wether is the answer is greater than 0 than I would say it is less than 0, or of your answers i would say d, I hope you explain

Answer 3

do it yourself

Answer 4

NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOoooooo