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Mathematics 8 Online
OpenStudy (mathmath333):

functions

OpenStudy (mathmath333):

\(\large \color{black}{\begin{align} &\normalsize \text{Find the maximim value of the function}\hspace{.33em}\\~\\ & \dfrac{1}{x^2-3x+2} \hspace{.33em}\\~\\ \end{align}}\)

OpenStudy (solomonzelman):

interval given ?

OpenStudy (solomonzelman):

with out interval this maximum value diverges to infinity.

OpenStudy (mathmath333):

this question means that i have to minimize \(\large \color{black}{\begin{align} x^2-3x+2 \hspace{.33em}\\~\\ \end{align}}\) right ?

OpenStudy (solomonzelman):

should be, or els... i mean there is not maximum value here, if you are taking over \((-\infty,~+\infty)\)

OpenStudy (solomonzelman):

wait

OpenStudy (solomonzelman):

1/that ? or, just that ?

OpenStudy (mathmath333):

lol its \(\large \color{black}{\begin{align} \dfrac{1}{x^2-3x+2} \hspace{.33em}\\~\\ \end{align}}\)

OpenStudy (solomonzelman):

\(\large\color{black}{ \displaystyle f(x)=\frac{1}{x^2-3x+2} }\) and you want to find absolute minimum, right?

OpenStudy (solomonzelman):

well, I can tell you that the limit as x approaches \(\pm\)infinity is going to be 0.

OpenStudy (solomonzelman):

we can plot, I am guessing it is something like |dw:1435010239497:dw|

OpenStudy (mathmath333):

i want to find the maximum value of this \(\large \color{black}{\begin{align} \dfrac{1}{x^2-3x+2} \hspace{.33em}\\~\\ \end{align}}\)

OpenStudy (solomonzelman):

none

OpenStudy (solomonzelman):

it is +infinity

OpenStudy (mathmath333):

but how ?

OpenStudy (solomonzelman):

https://www.desmos.com/calculator

OpenStudy (mathmath333):

how i prove that with algebra

OpenStudy (solomonzelman):

even the minimum doesn't exist.

OpenStudy (solomonzelman):

with algebra, even with no calc ?

OpenStudy (mathmath333):

idk calculus

OpenStudy (solomonzelman):

ic

OpenStudy (solomonzelman):

lets c

OpenStudy (solomonzelman):

\(\large\color{black}{ \displaystyle f(x)=\frac{1}{x^2-3x+2} }\) it has vertical asymptotes, can you find them for me?

OpenStudy (mathmath333):

\(\large \color{black}{\begin{align} x=2,\ 1 \hspace{.33em}\\~\\ \end{align}}\)

OpenStudy (solomonzelman):

yes

OpenStudy (solomonzelman):

and, the best thing I can see here is to use the idea of a limit to see where range tends to the close we get to x=1 and x=2. I don't really know a purely algebraic proof for why this function has no max or min.

OpenStudy (xapproachesinfinity):

that has a max actually

OpenStudy (solomonzelman):

yes?

OpenStudy (solomonzelman):

https://www.desmos.com/calculator keep scrollin up

OpenStudy (solomonzelman):

on a certain interval, no doubt (unless it has a domain gap)

OpenStudy (xapproachesinfinity):

i think it attains one max does not perhaps required any domain to get it or i think

OpenStudy (xapproachesinfinity):

your graph does not show up see here https://www.desmos.com/calculator

OpenStudy (solomonzelman):

i don't think there is a max. that is due to an asymptote - two of them, there.

OpenStudy (solomonzelman):

we can find the limit from the right and from the left as x approaches 1 and 2.

OpenStudy (xapproachesinfinity):

http://prntscr.com/7k4q1l here see that bottom part of the graph

OpenStudy (xapproachesinfinity):

with calculus we can prove it has a max value but @mathmath333 is looking for a different way

OpenStudy (solomonzelman):

this graph goes further down and up if you scroll on desmos, but we can go ahead and take any limit that is closed from either side of any of the asymptotes you wish to choose.....

OpenStudy (xapproachesinfinity):

i mean here local max not abolute of course

OpenStudy (mathmath333):

how to find that local max

OpenStudy (solomonzelman):

oh, but the question is asking for absolute doesn't it?

OpenStudy (solomonzelman):

that is what i would think of course

OpenStudy (xapproachesinfinity):

first let's write that as 1/(x-1)(x-2)

OpenStudy (xapproachesinfinity):

i had thought of absolute too, just not sure about it!

OpenStudy (mathmath333):

yes the question is asking absolute, i just asked that of curiosity

OpenStudy (solomonzelman):

this function is pretty weird. I wonder what would it model

OpenStudy (solomonzelman):

i mean in real world

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