1. f(x) < 0

f(x) > 0

If x < 0, then f(x) < 0

If x > 0, then f(x) > 0
The answer is 4 but i don’t know why. So if you gyzz could give me a good explanation it would really help. Thank you 😀
1 Answer

The first 2 you can dismiss completely because you can’t prove either one of those for all x (if x = 30, for instance, 1/3 * (30) + 9 = 10 + 9 = 1). In fact, let’s assume x = 3. Then 1/3 * (3) + 9 = 1 + 9 = 8. That alone also disproves C). D) is true for all x > 0, because if x = 0, you’d get 9, the minimum value under the subset.