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are my choices correct?


 Mar 22, 2019

If a function is positive the y-value is greater than 0; it's above the y-axis.

Can you retry? (one of the answer choices you said are right.)


You are very welcome!


 Mar 22, 2019

Do you mean that (4, ∞) should not be selected? I think that all my other selected choices have a y-value greater than 0.

Guest Mar 22, 2019

For each one, we check to see if any part of the interval is below the x-axis. If so, we do not check that one. For (-2, 0), we can tell that the whole function is negative, not positive. (An example is (-1, -1.475), where the y-coordinate is negative.) For (0, 4), by inspection, there is no part of the graph below the x-axis. For (4, ∞), we see that something like (5, y) is already way under the x axis, so this is not a choice. 


For (-∞, -2), we can see that all of it is above the x-axis. So, this is an option. For (2, 2.5), this includes the interval at the topmost part of the second curve. This is above the x-axis, so this is a choice. Finally, for (-1.5, -1), this is the bottommost part of the first curve, which is below the x-axis. So, this does not work.


So, our final answers are (0, 4), (-∞, -2), and (2, 2.5). (2nd, 4th, and 5th choices.)


~ asdf334

 Mar 22, 2019

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