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Mathematics 13 Online
OpenStudy (kramse18):

Help with series!!! Please!!

OpenStudy (kramse18):

Follow the steps below to find a power series representation for f(x)=8/x2+2x−3: 8/x2+2x−3=Ax−1+Bx+3 , where A = and B = . Find the first 4 non-zero terms in the power series representation of the following fractions: 1/x−1= +... 1/x+3= +... Therefore f(x)=8/x2+2x−3=c0+c1x+c2x2+... , where c0= , c1= , c2= , c3= .

OpenStudy (kramse18):

I have everything. I just can't figure out what c1,c2, or c3 is

OpenStudy (bobo-i-bo):

Could you make life easier by properly formatting everything please?

OpenStudy (kramse18):

Follow the steps below to find a power series representation for f(x)=8/x^2+2x−3: 8/x^2+2x−3=A/(x−1)+B/(x+3) , where A = and B = . Find the first 4 non-zero terms in the power series representation of the following fractions: 1/x−1= +... 1/x+3= +... Therefore f(x)=8/x^2+2x−3=c0+c1x+c2x2+... , where c0= , c1= , c2= , c3= .

OpenStudy (anonymous):

how many terms do you need?

OpenStudy (anonymous):

you got \[\frac{2}{x-1}-\frac{2}{x+3}\] or \[\frac{-2}{1-x}-\frac{2}{3+x}\] power series for the first one should be easy right?

OpenStudy (kramse18):

I need 4 terms. I have the first one as -8/3

OpenStudy (anonymous):

the power series expansion for \(\frac{1}{1-x}\) is well known write it down and multiply by -2

OpenStudy (anonymous):

as for \[\frac{2}{x+3}\] treat is as \[\frac{2}{3}\times \frac{1}{1+\frac{x}{3}}\]

OpenStudy (kramse18):

would the second term be -5/3

OpenStudy (anonymous):

i don't know, i didn't do it but the basis for all this is the following \[\frac{1}{1-x}=1+x+x^2+x^3+...\]

OpenStudy (anonymous):

multiply that by \(-2\) to get the power series for the first part of the decomposition

OpenStudy (kramse18):

that part I know

OpenStudy (anonymous):

for the second part, \[\frac{2}{3}\times \frac{1}{1+\frac{x}{3}}\] replace (x\) in \(\frac{1}{1-x}\) by \(\frac{x}{3}\)

OpenStudy (anonymous):

then multiply by \(\frac{2}{3}\)

OpenStudy (anonymous):

ok that was a mistake, replace \(x\) by \(-\frac{x}{3}\)

OpenStudy (anonymous):

you get \[\frac{2}{3}(1-\frac{x}{3}+\frac{x^2}{9}-\frac{x^3}{27}+...)\]

OpenStudy (anonymous):

that is the first 4 terms of the second part, add that to \[-2(1+x+x^2+x^3+x^4)\]

OpenStudy (kramse18):

says it is wrong....

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