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Wed 1 Oct, 2008 03:46 pm
Express (x^2+23)/((x+1)^3(x-2)) in partial fraction
@Lingqi,
Let me guess -- you want us to do totally your homework for you without showing anything you have done to try and solve ther problem on your own? Is that about right?
@Ragman,
No, its not that i hv done it but i'm lazy to type my working coz 2 long..My working is wrong so i jz wan 2 knw anybody knw alternate method to solve it..Jz doing some research..If got new method i learn more..If nt nevermind..Anyway my teacher wil explain it..Dont u think by doing this u might find easier ways to solve this questions than ur tcer method..I'm juz doing comparing..No offence..Sorry if i hv say o done anything wrng
@Lingqi,
Lingqi wrote:
Express (x^2+23)/((x+1)^3(x-2)) in partial fraction
In general, a fraction with n linear factors of x+1 in the denominator can be decomposed as follows:
A1/(x + 1) + A2/(x+1)^2 +...+ An/(x+1)^n
@Lingqi,
Lingqi wrote:
Express (x^2+23)/((x+1)^3(x-2)) in partial fraction
How come you didn't say "Please"?
Ok please anybody o miller can you all have a look what i have done..(x^2+23)/((x+1)^3(x-2))=a/(x+1)^3+ b/(x+1)^2 + c/(x+1) + d/(x-2)
=a(x-2) +b(x+1)(x-2)+ c(x+1)^2(x-2)+ d(x+1)^3
=(c+d)x^3+ (b+3d)x + (a-b-3c+3d)x^2 + (-2a-2b-2c+d)
comparing coefficient:
c+d=0 ->eqn 1, a-b-3c+3d=0 ->eqn 2, -2a-2b-2c+d=23 ->eqn 3, b+3d=1 ->eqn 4
put eqn 2=eqn 3: 3a+b-c+2d-23=0 ->eqn 5
put eqn 1=eqn 4: c+d= b+3d-1
-2d+ c- b+ 1=0 ->eqn 6
eqn 5 + eqn 6:
3a-22=0
3a=22
a=(22)/3
put a into eqn 5, b- c+ 2d-1=0
put eqn 1 into eqn 5 where c= -d, b-(-d)+2d-1=0
b+3d=1
please anybody know how to continue the rest & where i got wrong because the real answer is 1/(x-2) - 1/(x+1) -2/(x+1)^2 -8/(x+1)^3