Best answer:
The factored version that you gave shows that you need to check the intervals
(-infinity,-4), (-4,-1), (-1,1), and (1,+infinity), as each such interval will produce values that are either all positive or all negative. That's because the ONLY zeros are at -4, -1, and +1.
So, plug in x = -5, and what do you...
show more
Best answer: The factored version that you gave shows that you need to check the intervals
(-infinity,-4), (-4,-1), (-1,1), and (1,+infinity), as each such interval will produce values that are either all positive or all negative. That's because the ONLY zeros are at -4, -1, and +1.
So, plug in x = -5, and what do you get? I get -125 + 100 + 5 - 4 = -24. Therefore, the entire interval (-infinity,-4) will produce results less than 0, and it is NOT part of the solution set. Next, if I plug in x = -2, I get
-8 + 16 + 2 - 4 = +6, so the interval (-4,-1) is part of the solution set. Next, when x = 0 I get -4, so the interval (-1,1) is not part of the solution set. And finally, if I plug in x = 2, I get 8 + 16 - 2 - 4 = 18, so the interval (1,infinity is part of the solution set.
The whole solution set is
(-4,-1)U(+1,infinity).
6 answers
·
17 hours ago