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Mathematics 14 Online
OpenStudy (anonymous):

Least upper bound , Greatest lower bound

OpenStudy (anonymous):

@ganeshie8

ganeshie8 (ganeshie8):

https://www.youtube.com/watch?v=XgGzm0d_MDY

ganeshie8 (ganeshie8):

watch this quick, we can do an example after that :)

OpenStudy (anonymous):

I watched it >.<

OpenStudy (anonymous):

The same on u sent last night?

ganeshie8 (ganeshie8):

no, this is different and much better and short

ganeshie8 (ganeshie8):

7 minutes.... watch it :)

OpenStudy (anonymous):

Okay, So i have a feeling that -1 will be one of the answers because that is one of the factors that did not have remainder 0

OpenStudy (anonymous):

\[x^4+10x^3+33x^2+38x+8\]

ganeshie8 (ganeshie8):

yes, we have found roots for this already right ?

OpenStudy (anonymous):

Yes but we did not find bounds

OpenStudy (anonymous):

atleast i dont think we did

ganeshie8 (ganeshie8):

once we have roots, finding bounds is piece of cake

OpenStudy (anonymous):

Well lets bake a cake then! lol

ganeshie8 (ganeshie8):

lol, below are ur roots : \(\large -4, ~-2, ~-2-\sqrt{3}, -2 + \sqrt{3}\)

ganeshie8 (ganeshie8):

whats the lowest value ? whats the greatest value ?

ganeshie8 (ganeshie8):

the lowest value of roots is \(-4\), so the "greatest lower bound" is \(-4\)

ganeshie8 (ganeshie8):

the highest value of roots is \(-2 + \sqrt{3}\) so the "least upper bound" is \(-2 + \sqrt{3}\)

ganeshie8 (ganeshie8):

we're done.

ganeshie8 (ganeshie8):

let me knw if smthng doesnt make sense..

OpenStudy (anonymous):

Do you want ice cream with your cake?

OpenStudy (anonymous):

Because im going to reward myself for understand what you just said muhaha

OpenStudy (anonymous):

Shall we do another?

OpenStudy (anonymous):

Oh, you left ( ._.)

ganeshie8 (ganeshie8):

awww both are irresitables xD

ganeshie8 (ganeshie8):

sorry somebody knocked the door... had to attend to that lol

ganeshie8 (ganeshie8):

lets do the next q :)

OpenStudy (anonymous):

"Attend to that " sounds like you murdered them haha

ganeshie8 (ganeshie8):

lol hahah wish i could >.<

ganeshie8 (ganeshie8):

wats the next q ha ?

OpenStudy (anonymous):

Lol nice way to change the subject ;)

OpenStudy (anonymous):

sec itll take a second to type

ganeshie8 (ganeshie8):

:) take ur time

OpenStudy (anonymous):

\[p(x)=x^5+3x^4-9x^3-3x^2-52x-60\] we need to find : p q p/q # of positive roots # of negative rootss least upper bound greateest lower bound roots

ganeshie8 (ganeshie8):

evil professor :/

OpenStudy (anonymous):

seriously though. that 60 is about to make me cry

ganeshie8 (ganeshie8):

start by counting sign changes in p(x) and p(-x)

OpenStudy (anonymous):

1?

ganeshie8 (ganeshie8):

\(p(x)=x^5+3x^4-9x^3-3x^2-52x-60\) yes, sign changes in p(x) = 1 so there will be EXACTLY 1 positive real root for p(x)

ganeshie8 (ganeshie8):

next, find f(-x), and count the sign changes

OpenStudy (anonymous):

its either 2 or 6

OpenStudy (anonymous):

Is that not right?

ganeshie8 (ganeshie8):

\(p(x)=x^5+3x^4-9x^3-3x^2-52x-60 \) \(p(-x)=-x^5+3x^4+9x^3-3x^2+52x-60 \)

ganeshie8 (ganeshie8):

sign changes in p(-x) is 4 so there can be 4 or 2 or 0 negative real roots

OpenStudy (anonymous):

Yeah i knew that, I was just testing you

ganeshie8 (ganeshie8):

P = 60 Q = 1 P/Q = \(\pm 1, \pm 2, \pm 3, \pm 4, \pm 5, ......\)

OpenStudy (anonymous):

>.>

ganeshie8 (ganeshie8):

pick ur fav number +1 or -1 ?

OpenStudy (anonymous):

-1

ganeshie8 (ganeshie8):

\( \begin{array}{} -1|&1&3&-9&-3&-52&-60\\ &&&&\\ \hline &&&&\\ &1&&& \end{array} \)

OpenStudy (anonymous):

ill do it !

OpenStudy (anonymous):

|dw:1396543448725:dw|

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