So in calculus we have been doing absolute extrema and critical points and all that jazz, and it has raised a question. I had a question on my homework that asked what the maximum and minimum of a line would be on the closed interval [0,2], where f(x) = 7/4X - 3. The minimum was -3 and the max was 1/2. I then asked what the minimum was on the interval (0,2]. I said it was negative infinity, but it was counted wrong. According to my teacher, the minimum did not exist.
My reasoning for answering negative infinity is because technically the answer was - 2.9999... because the value would just keep approaching -3. Since infinity holds all numbers, I assumed that the value was infinite, because you could just keep adding 9's to the end of the decimal, and since the number was decreasing in value, I said negative infinity.
If someone could shed some light on why I am wrong, that would be great, because I am currently in an argument with my teacher about it.
[spoiler]Ahhh... it is nice to post on my computer again, it has been a while[/spoiler]
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Edited by Jotaro Kujo PhD: 11/6/2013 5:49:13 PMI'm pretty sure that -2.999... isn't considered undefined like negative infinity. It has a "known" value between -2.999 and -3. I'm not taking BC until next year, so I'm just guessing.