#Help

52 messages · Page 1 of 1 (latest)

ionic shale
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i have 8(x-2)/(x-4)(x+2) as my answer

help find the equation of this graph

crystal tundraBOT
leaden seal
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,w graph [8(x-2)]/[(x-4)(x+2)] from -10 to 10

leaden seal
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tis a bit off

ionic shale
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i have that answer currently just cant figuire it out

ionic shale
leaden seal
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a bit, im thinking how to modify what you already have to fix it but i got nothing

ionic shale
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yeah that what im saying shit just dont make sense

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this is the hardest ive ever been in my life

wintry gazelle
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You basically need to flip the sign of the graph when x > 4, you do not want any more zeros though so you should add a new factor in the denominator. Since you don't want any more asymptotes either you have to either use x-2, x+2, or x-4 again in the denominator, or multiple of them

wintry gazelle
# ionic shale wdym

Currently in 8(x-2)/(x-4)(x+2), when x > 4, 8(x-2)/(x-4)(x+2) > 0. Well we want values of our equation to be negative when x > 4, so we should multiply by something that will only change the sign when x > 4 right?

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In general when you add things to the numerator of a rational expression, you are changing the behavior of the solutions (when the equation = 0), and when you add things to the denominator, you are changing the behavior of the discontinuities. If you add a copy of a factor though, it does not change the behavior of the solutions/discontinuities, it only changes the behavior of the sign.

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For example lets say we add (x-5) to the numerator. This is the new graph we get. We see that the asymptotes stay the same, but we get a new root at x=5

ionic shale
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ok but that would make a new x intercept correct?

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but we only have 1

wintry gazelle
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Exactly

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So if we add anything to the numerator that is not (x-2) we get a new x intercept

ionic shale
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correct

wintry gazelle
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What happens if we add (x-2)?

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We get this graph

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It has the same behavior as before (same asymptotes and x-intercepts), but the sign of values if changed

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This is not quite what we want though because this doesn't flip the sign of the function ofr x>4, it does stuff around x=2, which is expected since we are multiplying by (x-2)

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If we want behavior to change around x = 4, we should multiply by something like (x-4) or 1/(x-4)

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This is because for x-4, when x>4, x-4 > 0, and when x<4, x-4 < 0

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This is the key to flipping the sign ONLY for values of x > 4

ionic shale
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so what woudl the answer be

wintry gazelle
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So now you should be thinking we either add (x-4) to the numerator or denominator, but from before we found adding (x-4) to the numerator would create a new x-intercept, which is not what we want, so instead we should consider adding (x-4) to the denominator

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Try adding (x-4) to the denominator and the answer will become clear

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Your solution will be of the form y = a(x-2)/(x+2)(x-4)(x-4) for some constant a

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Since I was trying not to give the entire answer away I gave a lot of information that might not have been clear, but my point was basically you should think about what happens when you add things of the form (x-a) to the numerator and denominator, and see what happens when you do that. Also since we want the behavior to change for x > 4, using a = 4 would be the most obvious choice to experiment with

ionic shale
wintry gazelle
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Yup

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Now its basically the original image but flipped and scaled

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so your gonna need to multiply by a negative constant to flip it vertically, then find the right scale factor

ionic shale
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yeah but now y intercept is not 0,2

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its 0,0.25

wintry gazelle
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Ok so you should multiply by some value a such that 0.25a = 2

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(multiply by 8)

ionic shale
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holy fuck

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ur a genius

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what math are u in

wintry gazelle
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Im in my last year of a math undergraduate program

ionic shale
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so what math is that

wintry gazelle
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Im taking real analysis, abstract algebra, complex analysis, linear algebra, and some other misc courses

chrome plover
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I mean I found the answer should I show it?

ionic shale
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sure

chrome plover
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What do you have currently or is it the same?

ionic shale
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i already have the answer

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what do u have

chrome plover