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Old 07-13-08, 02:49 PM   #1
phantomcow2
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Find f(-x)?


I am being prompted to find f(-x) of the following function:


So plug in -x for x.

(4*-x) + 1/(4*-x)

-4x + 1/(-4x)

Find a common denominator, which in this case is -4x. So, I multiplied the left term by (-4x)/(-4x)

This gives me 16x^2 + 1/(-4x)

Is that correct? I only have one attempt remaining in my web applet.
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Old 07-13-08, 03:20 PM   #2
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The correct answer is (16x^2 + 1)/(-4x). You omitted the parentheses in the numerator, though I'm sure it was just an oversight.
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Old 07-13-08, 04:43 PM   #3
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Okay, well I did get that right. Now how about this:


Find the domain.
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Old 07-13-08, 04:47 PM   #4
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I'm stumped. At first I thought the domain would be [3,INF]. The reason being that 3 is the minimum number which can be inputted into this function and still get a real number. THe reason being the sqrt(x-3)
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Old 07-14-08, 07:56 AM   #5
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That is the correct answer. Does your applet thingy (or whatever it is) say it's wrong?

(BTW, my creds: BA in math; am currently an editor of math textbooks)
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Old 07-14-08, 07:57 AM   #6
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If you're typing in [3,INF], try typing [3,INF), since technically, an interval that does off to infinity is open on that end, not closed.
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