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Mathematics 18 Online
OpenStudy (anonymous):

I will fan, medal, and give you a testimonial! I REALLY need help! Find a counterexample that disproves the following statement: (Picture Posted) A. x = 1 B. x = -2 C. x = 100 D. x = 5

OpenStudy (anonymous):

OpenStudy (anonymous):

Can someone please help?

OpenStudy (e.mccormick):

Well, what are a few values you could plug in? And have you looked at the graph of those?

OpenStudy (e.mccormick):

Oh, and with the choices, you could just try them.

OpenStudy (anonymous):

I plugged in all the answer choices but I'm not quite sure which one it is. :(

OpenStudy (e.mccormick):

Say x=.01 \(\dfrac{1}{.01}\le .01\implies \) \(100\le .01 \) Which is false. Do you see another in your list that would cause a false condition? When you plug them in, what do you get?

OpenStudy (anonymous):

When I plugged in 1, I still get 1, so that would be false too, right?

OpenStudy (e.mccormick):

\(1\le 1\) well, there is equal. And \(1=1\) so true.

OpenStudy (e.mccormick):

That is the first one, now move to the second. Try it and what do you get?

OpenStudy (anonymous):

Oh oops, I meant true. And for the second one I got -0.5.

OpenStudy (e.mccormick):

OK. \(-.5\le -2\) is that true?

OpenStudy (anonymous):

No

OpenStudy (e.mccormick):

So there is the counter example.

OpenStudy (anonymous):

Oh okay.. Thank you for explaining it. :)

OpenStudy (e.mccormick):

To be honest, it is true \(x \ge 1\) and between 0 and -1, including -1. I'll show a graph that also shows why.

OpenStudy (e.mccormick):

https://www.desmos.com/calculator/l9rtpnywx1 See how it gets all funny between -1 and 1? That is why this happens.

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